v2.2.1. Bugfix. Improvement.

- v2.2.1 June 24, 2013
	- `determinePossibleExecPath` is now more effecient
	- `getGitPath`, `getNodePath`, `getNpmPath` won't added `undefined`
paths
	- `spawn`
		- will now inherit our `process.env` by default, can be changed with
`opts.env`
		- will now send `signal` and `code` in the completion callback
correctly
		- now works
	- `getExecPath`
		- now caches the result
		- won't currupt absolute paths
		- will work with relative paths