testOnErrorMustBeDefined
testOnIsAKeyword
testErrorIsAKeyword
testOnErrorCanBeAddedToTheEndOfAnAssertion
testOnErrorIsReturnedWhenLocatingTheMatcher
testOnErrorIsNotReturnedIfNotInTheSyntax
testOnErrorIsReturnedFromData
testOnErrorMustBeTheLastData
testCanSetCustomFailureMessage
testWillFailWithCustomMessage
testWillUseOnErrorMessage
Ignore wiki
Merge branch 'release/1.3' of https://github.com/elliotchance/concise into 1.3/83-on-error-clause

Conflicts:
	wiki
Merge pull request #83 from elliotchance/1.3/83-on-error-clause

"on error" clause for custom assertion messages