Added beEmpty() Nimble matcher
Refactored beEmpty() matcher spec
Replaced occurrences of ‘not to’ with ‘to not’ in order to match the matcher pattern <expect().toNot.>
Prepended privately used constant with underscore
Changed `to not` to `not to`
Reintroduced variation in `notTo` and `toNot` methods
Added ObjC support for beEmpty()
Merge branch 'is-empty' of github.com:endersstocker/Quick into endersstocker-is-empty
NSObject+Flatten: consolidate flattening logic

- DRY out flattening code
- Use (perhaps more idiomatic?) switch statement in BeEmpty
Merge branch 'endersstocker-is-empty'

Conflicts:
	Nimble/Nimble/Matchers/Contain.swift
	Nimble/NimbleTests/Matchers/ContainSpec.swift