Get event listener inside of the infoWindow

* It's not possible to trigger an event for the 'show directions' link
  when it is clicked in the info window.
* This involved creating a new view for the infoWindow content, which
  adds the link to the div of the info window. Since the parent element
  is created at the time of the infowindowview creation, the 'showDirections'
  function inside of the pin view can be triggered.

Next steps:
*  Have the showDirections function actually create a directions list
Merge pull request #12 from mknudsen01/add-listener-to-pin-link

Add listener to pin link
Add route to map when click 'Get Directions'

* Creates a DirectionsView that implements a Google Maps
  DirectionsRenderer
  [Directions Service](https://developers.google.com/maps/documentation/javascript/directions)
* Takes the current destination and displays a route to the marker
  that was clicked

Next Steps:
* The renderer creates a new pin that's in a slightly different
  location from the original pin. Will either need to hide it or
  remove it
* Also need to create a way to display the route directions step
  by step