Add clang flags to travis environment

Trying to fix the building on travis...

Author: brianc

.travis.yml

@@ -3,7 +3,7 @@ sudo: false
 before_script:
   - node script/create-test-tables.js pg://postgres@127.0.0.1:5432/postgres
 env:
-  - PGUSER=postgres PGDATABASE=postgres
+  - CC=clang CXX=clang++ npm_config_clang=1 PGUSER=postgres PGDATABASE=postgres
 
 addons:
   apt: