close jonschlinkert/strip-comments#5

- remove `.safeBlock` and `.banner` methods
- `.banner` is removed, cuz of  [strip-banner](https://github.com/jonschlinkert/strip-banner)
- refactoring
- new api doc

Don't forget to edit your strip-banner module ;] You can use some of regexes from here without `g` modifier. I think this will work `var re = new RegExp(reBlock + reBlockEnd, 'm');`