* Added user counters, and move use of bytes_processed and items_processed to user counter logic.

Each counter is a string-value pair. The counters were
made available through the State class. Two helper virtual
methods were added to the Fixture class to allow convenient
initialization and termination of the counters: InitState()
and TerminateState(). The reporting of the counters is buggy
and is still a work in progress, to be completed in the next commits.

* fix bad removal of BenchmarkCounters code during the merge

* add myself to AUTHORS/CONTRIBUTORS

* fix printing to std::cout in csv_reporter

* bytes_per_second and items_per_second are now in the UserCounters class

* add user counters to json reporter

* moving bytes_per_second and items_per_second to their old state

* console reporter dealing ok with user counters.

* update unit tests for user counters

* CSVReporter now prints user counters too.

* cleanup user counters

* reverted changes to cmake files which should have gone into later commits

* fixture_test: fix gcc 4.6 compilation

* remove ctor with default argument

see https://github.com/google/benchmark/pull/262#discussion_r72298055

* use (auto-defined) BENCHMARK_HAS_CXX11 instead of BENCHMARK_INITLIST.

https://github.com/google/benchmark/pull/262#discussion_r72298310

* leanify counters API

Discussions:
API complexity: https://github.com/google/benchmark/pull/262#discussion_r72298731
remove std::string dependency (WIP): https://github.com/google/benchmark/pull/262#discussion_r72298142
spacing & alignment: https://github.com/google/benchmark/pull/262#discussion_r72298422

* remove std::string dependency on public API - changed counter name storage to char*

* Counter ctor: use overloads instead of default arguments

discussion:
https://github.com/google/benchmark/pull/262#discussion_r72298055

* Use raw pointers to remove dependency on std::vector from public API .

For more info, see discussion at https://github.com/google/benchmark/pull/262#discussion_r72319678 .

* Move counter implementation from benchmark.cc to counter.cc.

    See discussion: https://github.com/google/benchmark/pull/262#discussion_r72298980 .

* Remove unused (commented-out) code.

* Moved thread counters to ThreadStats.

* Counters: fixed copy and move constructors.

* Counter: use an inplace buffer for small names.

* benchmark_test: move counters test out of CXX11 preprocessor conditional.

* Counter: fix VS2013 compilation error in char[] initialization.

* Fix typo.

* Expose counters from State.

See discussion: https://github.com/google/benchmark/pull/262#issuecomment-237156951

* Changed counters interface to map-like.

* Fix printing of user counters in ConsoleReporter.

* Applied clang-format to counter.cc and console_reporter.cc.

Command was `clang-format -style=Google -i counter.cc console_reporter.cc`
I also applied to all other files, but the changes were very
far-reaching so I rolled those back.

* Rename Counter::Flags_e to Counter::Flags

* Fix use of reserved names in Counter and BenchmarkCounters.

* Counter: Fix move ctor bug + change order of members.

* Fixture: remove tentative methods InitState() and TerminateState().

* Update fixture_test to the new Fixture interface.

* BenchmarkCounters: fixed a bug in the move ctor. Remove call to CHECK_LT().

CHECK_LT() was making the size_t lookup take ~double the time of a string lookup!

* BenchmarkCounters: add option to not print zero counters (defaults to false).

* Add test to compare counter storage and access with std::map.

* README: clarify cost of counter access modes.

* move counter access test to an own test.

* BenchmarkCounters: add move Insert()

* Counters access test: add accelerated lookup by name.

* Fix old range syntax.

* Fix missing include of cstdio

* Fix Visual Studio warning

* VS2013 and lower: fix use of snprintf()

* VS2013: fix use of char[] as a member of std::pair<>.

* change counter storage to std::map

* Remove skipZeroCounters logic

* Fix VS compilation error.

* Implemented request changes to PR #262.

* PR #262: More requested changes.

* README: cleanup counter text.

* PR #262: remove clang-format changes for preexisting code

* Complexity+Counters: fix counter flags which were being ignored.

* Document all Counter::Flag members

* fixed loss of counter values

* ConsoleReporter: remove tabular printing of user counters.

* ConsoleReporter: header printing should not be contingent on user counter names.

* Minor white space and alignment fixes.

* cxx03_test + counters: reuse the BM_empty() function.

* user counters: add note to README on how counters are gathered across threads