Brush up project

[mre]

It's been a while since I looked at this code. Most likely, it would need some love from an eager PHP developer to be up to the latest coding standards.

If anyone wants to tackle this, just add a comment here or create a pull request right away. I can provide mentorship.

[mre]

@Douglasdc3 had a few more suggestions in #7:

PSR-2 naming conventions for methods and variables
avoid public accessor api on Dropbox object instead use create wrapper methods for the ones you need on Dropbox class
Upgrade to minimum PHP 5.6 and use short array syntax
Change the namespace and add PSR-4 autoloading suggestion could be Mre\Unicorn