Merge pull request #42 from nikicat/master

Image: removed repo parsing hueristics, remved automagic rebuilding
Bump version: 7.0 → 7.1
utils: added resource_string function
Ship: cache getssh result
SourceImage: reset id after build
Shipment: add backref to self into ships
SourceImage: serialize files to yaml with content
migrated from docopt to click