Ability to specify method name as a title

- Now it is possible to set title to a return value of a method of a
router. It is useful to keep title computation logic away from titles
to keep them clean.
- Readme updated to cover new changes. Added instructions to
contribute. DRYed code in topic about super class in initialize
function.
Merge branch 'function-lookup' of https://github.com/romanenko/Backbonejs-Router-Title-Helper into function-lookup