[SAMPLE]: Both GPS & valid street address in tags
Reverse geocode bugfixes

- don't try to reverse geocode when we have empty GPS coordinates;
- don't fail when reverse geocode fails
Added reverse geocode example from Google Maps API
Rename: has_full_address? to have_full_address?
Changed tag parsing regex to eliminate leading & trailing spaces
get_tag() now returns canonical values
Don't need to call parse explicitly: it will be called after successful object creation
removed incorrect rspec syntax
renamed tests
Major refactoring for get_full_address()