Add directions view.

Show directions list when location list item tapped, and show map view when location list item
map button is tapped.  Also open directions list when map popup tapped.
Refactor Google Directions model classes
Merge in map directions
Alert user if map cannot be shown due to no Play services
Check for Internet connectivity.

Check before querying API, and quit app if no connection found.
Use URI builder to build Civic API query string
Update README; tidying
Perform distance calculation in geocode async task
Bump minimum SDK version to 16.

This will allow us to use otherwise deprecated call in Maps fragment, causing Travis to fail.
Added geocoding error handling
Linting
Set min SDK back to 15 and check version number in ViewTreeObserverCall.

Also more linting and linter warning suppression.
Merge pull request #22 from flibbertigibbet/feature/make-robust

Feature/make robust
Add election picker to home view

The behaviour is as such:

If there are other elections in the response,
display the election picker and make another
voterInfo query with the same address when the user selects
another election.

Removes the election picker from view when a voterinfo query
is received that has no other elections in its response.

Added a few tests for VoterInfo/Elections models