Removing custom fields test

This no longer seems supported by the Base API, so it seems useless
to have a test for it.
Adding map

Even though collect is already there, not having this convenience
method is somewhat confusing.
Incrementing version numbers.
Added pagination

As per the Base API docs, Deals and Contacts are paginated to 20 entries

http://dev.futuresimple.com/api/methods/deals-index

Simple logic is added that increments the page number if a new page is
necessary or available.
Fixed minor bug in deal_spec

entity has now been renamed, updated tests accordingly
That p shouldn't be there.
Cleaned up code to make it a bit more readable.
Actually that was a little too clever.
Merge pull request #7 from kanerogers/master

Pagination does not work in 0.4.2