Use /usr/bin/env node

Use __dirname to require local lib files
Don't return on no ~/.pushfile.json is available

This was causing the rest of the code to not evaluate, thus not allowing
the exported object to have the `createConfig` function.
Modifying description slightly.

User would need to set up short url in config to actually get a short url.
Version bump and adding Will as Contributor
URL isn't necessarily short...
Merge pull request #6 from wlaurance/exported-lib

Exported lib
version bump