Readme fixes
Add summary and dependencies in gemspec
Rename Llt to LLT on all fronts
Temporarily comment llt-diff dependency

It is not formally released so far. While we want to get it through the
git source in the Gemfile anyway, bundler would start to complain.
Add git dependencies to Gemfile
Better to use the new name llt-review...
Use jruby-1.7.10 in travis