Fix SetLabel usage example

Fix missing include in map_test.cc

building with libc++.

Pass const State to Fixture::TearDown. Fix memory leak in fixture_test

Format json in README.md

Pass const state to Fixture::SetUp. Add map_test.

Add number of threads to State.

Having access to the thread count from within a benchmark is useful,
for when one wants to distribute a workload dynamically among the
benchmarks running in parallel e.g when using ThreadRange() or
ThreadPerCpu().

Add section on optimisations to README

Add aarch64 support to src/cycleclock.h.

Fix ARM /proc/cpuinfo parsing.

Support MSVC on appveyor

Also fix related warning message typos.

From google3's base/cycleclock.

Update README to mention UseRealTime for wallclock time measurements.

Also adding a use case in the API header.

Fixes #170

Fixes #165: CustomArguments ret type in README

* adds myself to AUTHORS/CONTRIBUTORS

Fixes #159: Add inclusion of cstdio to files using stdout, printf and etc.

add static_cast to get rid of warnings for intel compiler on linux platform

Fix get_git_version to use GIT_EXECUTABLE.

get_git_version CMake function uses 'git' command directly, instead of
GIT_EXECUTABLE variable. This causes CMake errors while generating
project files in environments, where 'git' command is not present
in PATH.

Fixes #144  CMake fails without Git 

Android fix