Replace event listener with backbone event api

[jhwohlgemuth]

Description of Changes:

Replace eventListener.js with "refurbished" Backbone.Events

That is, the new event API is:

• addEventListener --> on
• removeEventListener --> off
• triggerEvent --> trigger

with additional capabilities:

• once
• listenTo
• listenToOnce
• stopListening

Related Issues:

• none

[coveralls]

Coverage decreased (-0.3%) to 95.822% when pulling f7ad797 on feature/replace-eventListener-with-backbone-event-api into bb9ad03 on master.

[coveralls]

Coverage decreased (-0.3%) to 95.811% when pulling 5ff98ad on feature/replace-eventListener-with-backbone-event-api into bb9ad03 on master.

[jhwohlgemuth]

Replace eventListener code with Backbone.Events

[coveralls]

Coverage decreased (-0.3%) to 95.791% when pulling 19ad1af on feature/replace-eventListener-with-backbone-event-api into bb9ad03 on master.

[coveralls]

Coverage increased (+0.2%) to 96.344% when pulling f6889a1 on feature/replace-eventListener-with-backbone-event-api into bb9ad03 on master.