add test methods for proplist
fix SvnRepo.proplist() for Subversion 1.8+ (issue #51)
factor out VCSRepo._command into function

Use this instead of depending on subprocess.check_output() in anyvcs/svn.py
Merge branch 'develop' into feature/issue/51

Conflicts:
	tests.py
Merge pull request #57 from OEP/feature/issue/51

Fix SvnRepo.proplist() for Subversion 1.8+ (issue #51)