[RFC] Upgrades Gmaps4rails

We're blocked on our rails 4.1 branches with failing jasmine test suites. In this past, we relied on a hack to get jasmine working with version 1.5.6 of gem `gmaps4rails`([commit](https://github.com/AgileVentures/LocalSupport/commit/99fc4bf7239806b7864dcedab5a9cd8198b0661b)), but this no longer seems to work with rails 4.1. Rather than extend the hack, let's just upgrade our `gmaps4rails` gem.

[Staged here](https://gmaps-upgrade.herokuapp.com/).

TODO:
- [x] get new maps working
- [x] configure map options (center, infowindow)
- [x] update rspec
- [x] update cucumber
- [x] DELETE JASMINE RAKE TASK!
OK, I just extracted the shared logic to MapMarkerJson