Global leak detected: i

Got mocha error because of the missing 'var' statement
Merge pull request #516 from mike-zenith/patch-2

Global leak detected: i
Enabling third-party drivers

Added a method and some documentation for plugging in a third-party driver for `orm2`.

Conflicts:
	.gitignore
Terminology change from Driver to Adapter

Updated terminology, where third-party database adapters are now called Adapters instead of Drivers.