Add until function to the condition object

until() works exactly like it's expected to: it executes a callback
function until the condition function returns a truthy value.
Add tests for condition.until()
Add documentation for until()
Add more verbose docs for asynchronous conditions
Merge pull request #11 from nathggns/whatyouhide-until

Whatyouhide until
Version 1.2.0
Merge branch 'master' into development