feat($parse): support the ternary/conditional operator

Closes #272
fix(ng-class): exportExpressionAttrs for ng-class, ng-class-odd, ng-class-even
chore(.agignore): add .agignore to prune command line searches

I use the Ag tool (like ack, grep, etc. - ref
https://github.com/ggreer/the_silver_searcher) for searching.  The
.agignore file is used to prune the search space.
feat($parse): support the integer division operator

Closes #233