Add directories to CtrlP's ignore list.

Add additional directories to CtrlP's ignore list within .vimrc.

The directories include:
* coverage - We want to ignore the coverage directory typically used for
storing coverage reports generated by build systems.
* .temp - We use the `.temp` directory to store files generated by unit
tests for Yeoman generators. The directory is configurable, but we've
chosen to use `.temp`.