Fix builds to install dev dependencies

Author: Ryan Munro

.travis.yml

@@ -40,7 +40,7 @@ before_install:
     - source ~/.nvm/nvm.sh
     - nvm install $NODE_VERSION
 install:
-    - npm install
+    - npm install -d
 before_script:
     - python -V
     - node --version

appveyor.yml

@@ -20,7 +20,7 @@ install:
   - "python --version"
   - "node --version"
   - "npm --version"
-  - "npm install"
+  - "npm install -d"
 
 test_script:
   - "npm test"