Allow to keep the build dir after succesful build

Set the option cleanupbuild to False to keep the build dir after a
succesful build. Can be helpfull for debugging purposes.
add import test for pysvn, print message if tests are being skipped
don't raise pysvn.ClientError, just try referencing it
fix SvnRepository test
Merge pull request #1 from boegel/repository

add additional unit tests, fix bugs in GitRepository and SvnRepository, code cleanup
Merge pull request #919 from boegel/no_debug_logging_tests

disable debug logging for unit tests
remove unused constants
style fixes
Merge pull request #2 from boegel/repository

minor style fixes
Merge pull request #913 from mesocentrefc/repository

Add custom repository type
add support for fetching easyconfigs from a PR via eb --from-pr
add unit test for --from-pr
make sure PR is in a 'clean' mergeable state
fix using post with authentication in agithub module
add --github-token, --github-user and --test-easyconfigs-pr command line options
add functions to create a gist and post a comment in an issue
implement support for reporting back with PR test result
fix typo
fix another typo
add support for fetching GitHub token from keyring