Added looping on install, giving mongod time to start.

During the install phase, if mongod hadn't completed startup, the call to add the admin user would fail and prevent the user from executing commands.  This fix will loop for a maximum of 200 seconds trying to connect and create the admin user.  Fixes #18.
Don't force mongodb on standard port, add command to connect to mongodb console as admin
Merge branch 'master' of github.com:jeffutter/dokku-mongodb-plugin
Update README.md
Merge pull request #19 from farmetha/connectionTimeout

Added looping on install, giving mongod time to start.
use mongodb:link on pre-release to set ENV vars
chmod pre-release
Change how ENV vars are set on link to avoid loop
Refactor ENV var setting in mongodb:link
fix typo