0.0.18 - Better template helpers

## NEXT STEPS
- [x] fix the url/path/realPath/directory mess: one word should always mean the same thing
- [ ] implement base helper class, with specs: https://github.com/adamrenklint/asimov/issues/43
- [ ] __specs to prove that the context and url is always what we would expect__
- [ ] implement common helpers: https://github.com/adamrenklint/asimov/issues/38

## KEYWORD DEFINITIONS

- __renderPage__ the page context currently being rendered.
- __renderContext__ the context currently being rendered. if not set, the current _renderPage_.
- __id__ an absolute url, relative to the top-level folder. used for key-value mapping in node maps. unique among all _nodes_.
- __url__ the _node_'s url, relative to _renderPage_. only available inside template helpers (and the page template/partials?).
- __path__ a system path.

## HELPERS

https://github.com/epeli/underscore.string
http://there4development.com/blog/2012/07/29/handlebars-helpers-for-debugging-and-pluralization/
https://github.com/elving/swag/tree/master/src
https://github.com/danharper/Handlebars-Helpers
https://github.com/raDiesle/Handlebars.js-helpers-collection#formatDate
http://thehungrycoder.com/general/handlebars-helpers.html

## BUILDING (CUSTOM) HELPERS SHOULD BE EASY!

- there should be no chance of fucking up the context
- there should be no chance of using an incorrect url
- there should be minimal boilerplate, i.e. functionality abstracted in utils
- access to arguments, options and the callback should be seamless