chore: remove gitter integration

No change to logic.

This removes gitter integration with the project. I don't monitor gitter
right now, and I've never noticed the integration to be particularly
useful otherwise.

Test: N/A

.travis.yml

@@ -8,8 +8,7 @@ env:
   - NODE_VERSION="8"
   - NODE_VERSION="9"
 
-# keep this blank to make sure there are no before_install steps
-before_install:
+before_install: null
 
 install:
   - rm -rf ~/.nvm
@@ -24,18 +23,10 @@ os:
   - osx
 script:
   - npm test
-  # make sure when the docs are generated nothing changes (a.k.a. the docs have already been generated)
   - npm run gendocs
   - npm run after-travis "Make sure to generate docs!"
 after_success:
   - npm run codecov -- -f coverage/lcov.info
 
-# Gitter
 notifications:
   email: false
-  webhooks:
-    urls:
-      - https://webhooks.gitter.im/e/743dc6b83b6dd05111ee
-    on_success: change  # options: [always|never|change] default: always
-    on_failure: always  # options: [always|never|change] default: always
-    on_start: never     # options: [always|never|change] default: always