Update .travis.yml

Don't install a particular version of npm

Author: brianc

.travis.yml

@@ -3,5 +3,3 @@ node_js:
   - "0.10"
 before_script:
   - node script/create-test-tables.js pg://postgres@127.0.0.1:5432/postgres
-before_install:
-  - npm install -g npm@~1.4.6