Switch to more reliable travis build; switch to pulp

- The trusty image has more juice apparently; switching to this results
  in a much faster, more reliable build, and seems to solve the problem
  where about 90% of the time, psc reports no output for more than 10
  minutes.

- Use pulp instead of gulp, since pulp is easier and it doesn't appear
  that we're getting anything special from gulp at this point.

Author: jonsterling

.travis.yml

@@ -1,9 +1,10 @@
 language: node_js
-sudo: false
+dist: trusty
+sudo: required
 node_js:
-  - 4
+  - 5
 install:
-  - npm install gulp bower -g
+  - npm install pulp bower -g
   - npm install && bower install
 script:
-  - gulp test
+  - pulp test

gulpfile.js

@@ -1,10 +1,6 @@
 {
   "private": true,
   "devDependencies": {
-    "gulp": "^3.9.0",
-    "gulp-purescript": "^0.7.0",
-    "gulp-run": "^1.6.8",
-    "purescript": "^0.7.6",
-    "run-sequence": "^1.1.1"
+    "purescript": "^0.7.6"
   }
 }