Move state out of browser.
Merge pull request #207 from kadams54/state-module

Try some stuff that changes the state: search in the sidebar, view charm details, minimize the sidebar, click on home, etc. Make sure nothing goes boom.

**Note:** some of the naming leaves something to be desired (i.e., `browser.state.view`, which is not actually a view, but rather the state of the current view) but that'll be addressed that in a subsequent branch.