POSIX filesystem wrapper example.
Added coverage report generation.
Coverage meter and 100% coverage.
Added append/truncate, GetSize() and tests.
Comment nit.
Style nit.
CR: Minor comments.
CR: More efficient file read.
CR: Verifying the trainling slash is there.
CR: s/unlink()/remove()/.
Merge pull request #4 from dkorolev/LinuxFileSystem

Linux/POSIX file system wrapper.
3Party -> 3party and a cleaner Makefile.
Merge pull request #5 from dkorolev/Cereal

3Party -> 3party and a cleaner Makefile.
Merge conflict.