Use git dependencies in Gemfile for llt-* gems.

Later the published gems should be used. This is prepared in the
gemspec. For local development see
http://bundler.io/v1.3/bundle_config.html.
Use https urls to git repositories.
Fixes homepage url.
Merge pull request #1 from latin-language-toolkit/llt_dependencies

Use git dependencies in Gemfile for llt-* gems.