Reactivate backward compatibility with C++03.
Add code coverage with Coveralls.
Build `Core_Timer` test if MSVC has C++11.
Install lcov and coveralls-lcov.

They were missing.
Build project in debug mode.
Add Coveralls badge to `README.md`.
Put badge side by side.
Rewording.
Merge pull request #139 from DO-CV/enh-add-code-coverage

[ENH] Set up coverage report in Coveralls.