import podspec
handle the case when one of the superviews is nil (i.e. we're working on the top view)
support the none attribute; replace exceptions with asserts
let -[UIView constrain:to:] return NSLayoutConstraint for debugging purposes
recognize subtraction operator. now you can do this:

    [button constrain:@"right = right - 10" to:view];
    [button constrain:@"bottom = bottom - 10" to:view];
Merge branch 'negativeconstants'
Conforming code to style, removing assert that will never be false

- All other if statements have curly braces
- If the regex is successfully matched, the NSAssert will never be false
- Adding '-' to documentation
Breaking out common regex constructs

Attempting to make regexes more generally readable
Adding labels to regex group indexes