Contain matcher
BeEmpty matcher
NSArray and NSSet support for contain matcher
Add Contain and BeEmpty files to spec target
Fix contain matcher for strings
Public modifiers for Contain and BeEmpty matchers
BeginWith matcher
EndWith matcher
Move container matchers spec files to appropriate folder
Exctract NSContainer protocols to a separate file
Rename 'NSContainer'->'SleipnirContainer'
Merge branch 'container_matchers'