refactor and reorganize view trigger and entity events unit tests

[wesmangum]

Proposed changes

• Import dependencies to move away from using global ones
• Use let in favor of this in beforeEach

Link to the issue: #3248

This pr is a small part of the work to refactor the whole unit tests directory. Merging this issue should keep #3248 open

[coveralls]

Coverage decreased (-72.1%) to 27.899% when pulling 8fa15a6 on wesmangum:tests/viewEntityEvents-viewTriggers into 91ab7ea on marionettejs:next.

[coveralls]

Coverage remained the same at 100.0% when pulling f4a3c0e on wesmangum:tests/viewEntityEvents-viewTriggers into 91ab7ea on marionettejs:next.

[paulfalgout]

Hopefully we can remove this import entirely

[coveralls]

Coverage remained the same at 100.0% when pulling 0e668bb on wesmangum:tests/viewEntityEvents-viewTriggers into 7761081 on marionettejs:next.

[coveralls]

Coverage remained the same at 100.0% when pulling 24eeb7e on wesmangum:tests/viewEntityEvents-viewTriggers into 5813ed2 on marionettejs:next.