Docs: Add documentation for the cell() and cells() API methods
New: Api methods - to$, toJQuery and join

- to$ - Convert the result set to a jQuery object. Compliment to the
  toArray method. This is mainly useful when working with the node() and
  nodes() methods.

- toJQuery - Alias of to$

- join - Array join method
Fix - API: Errors in plurals and signular forms of method naming