Add test for version output file
Move to the folder contraining the version file before calling git describe

This commit should fix #122 by ensuring the git describe command is called
from the folder containing RELEASE-VERSION. This should prevent `git describe`
to read the version from another Git repository and overwrite the scc version.
Add tests for RELEASE-VERSION file existence

- Rename existing RELEASE-VERSION at the beginning of test and restore it
at the end
- Check RELEASE-VERSION does not exist before running version tests
- Check RELEASE-VERSION is created before opening it
ADd unit test for version file overwriting
Add test for `scc version` command outside a Git repository
Use abspath when computing version_file location
Add unit test for scc version called from another Git repository
Remove test description
Merge pull request #122 from sbesson/122_version_fix

scc version is overwritten when called from a Git repository