Default Karama to single run mode
Move coveralls into a Travis-only task

Since Travis calls `npm test`, keep it reserved for Travis and default it to
`grunt travis`.

Add optional targets to `grunt test` to call a specific suite (`grunt
test:unit`, `grunt test:e2e`).
Merge pull request #82 from tlvince/bug/coveralls-travis-only

Move coveralls into a Travis-only task