chore: bump dependency versions, use nyc instead of istanbul

Author: nknapp

.gitignore

@@ -2,4 +2,5 @@ node_modules
 coverage
 *.iml
 /test-output/
-/test/fixtures/scenarios/*/actual
+/test/fixtures/scenarios/*/actual
+/.nyc_output

.travis.yml

@@ -11,4 +11,4 @@ script:
   - eslint --max-warnings 0 .
 after_script:
   - npm install coveralls
-  - cat ./coverage/lcov.info | coveralls
+  - nyc report --reporter=text-lcov | coveralls