[CHORE] Add yml config for Travis CI.
[CHORE] Add postgres addon to .travis.yml.
[CHORE] Add DATABASE_URL env and "grunt" to Travis.
[DOC] Add Travis build status image to README.
[CHORE] Add global pg module to travis.

[BUG] Move global pg install to before_install script.
[CHORE] create test database in Travis.
[CHORE] Move create test db in Travis to before_install.
[CHORE] Extract dbMigrateUp into Grunfile function
Merge pull request #56 from ripple/travis-ci

Travis CI