Merge branch 'release/v0.3.1' into develop
Extract constraint creation to separate method

Client code can handle adding and removing constraints manually.
New method in UIView category to easily add constraint(s)

New -addConstraintToCommonSuperview:
New -addConstraintsToCommonSuperview: (note the 's')
Refactored -commonAncestor: to -commonSuperview:. The former is now
deprecated, but still works.
New methods to easily remove constraint(s)

New -removeConstraintFromCommonSuperview:
New -removeConstraintsFromCommonSuperview: (note the 's')
Version bump
Merge branch 'release/v0.3.2'