Limit markers to past month and add toggle buttons

* Fetch incidents from past month rather than all incidents
* Add toggle button for future ability to switch map views
* Style toggle button
Add heatmap view

* Add ability to view heatmap in place of markers
* Move JS into separate JS file
* Improve implementation of Sass
Edit button styling and add google fonts gem

* Implement google fonts through gem
* Slightly edit button styling
* Improve JS implementation