highlight multiple lines

We can now highlight multiple lines, adding #L1-L2 to the hash.
We can select the ending line with shift + click.

Closes travis-ci/travis-ci#1829
Update log.js
Add ember.prod.js
Use ember.prod.js when compiling for production

For some reason uflify fails on regular ember.js build. Using production
build fixes the problem and we should do it anyway - our assets pipeline
does some debug version cleaning, but I'm not sure if it's still
compatible with what's done when generating Ember's production build.
extract the log lines selector into a separate component
store the last selected line and use it as the other end for multiple selection
Merge pull request #240 from dmathieu/multiple_lines

Highlight multiple lines
Merge branch 'master' of https://github.com/travis-ci/travis-web into updated-styles