WIP: use diff

Author: IgorMinar

Diff for: .travis.yml

@@ -45,8 +45,7 @@ install:
   # Log HTTP requests
   - npm config set loglevel http
   - npm install -g npm@2.5
-  - md5sum npm-shrinkwrap.json
-  - if [[  `md5sum npm-shrinkwrap.json` == `md5sum node_modules/npm-shrinkwrap.ng-hack.json` ]]; then echo "shrinkwrap changed. blowing away node_modules"; rm -rf node_modules; fi
+  - diff -q npm-shrinkwrap.json npm-shrinkwrap.json; if [[ $? -ne 0 ]]; then echo "shrinkwrap changed. blowing away node_modules"; rm -rf node_modules; fi
   - time npm install
   - cp npm-shrinkwrap.json node_modules/npm-shrinkwrap.ng-hack.json