pep8 fixes
Renamed doc to docs, enabled extentions for tox tests
Added tox config for automating tests
pep8 fix
Updated test to handle changes to map_field
Updated tox config to get tests working with pypy
Merge branch 'master' into development
Merge branch 'master' into development
Added new feature of mappings, to map to lists.

Map actions can return iterators to the mapper which can convert them into valid lists.
Removed extraneous imports
Remove redundant method and simplify mapping rule generation code.
Add additional tests for mapping, covering:
- map_list_field decorator and it's operation
- the situation where a target field that is in the source resource, but a value from a different field is required (see the same_but_different field in test cases for an example of this)
Changed pep8 check to limit line length to 120chars, the default value for PyCharm
Added cached_property decorator for properties that do lazy generation of values that don't change.
Added build directory to those ignored by flake8
Pass on __init__ attribute assume_local's value
Simplify methods and use lamba expressions
Updated documentation on Field class, added new doc_text option, this is intended to replace help_text
Updated doc gen to use new doc_text attribute on fields
Major update of documentation.

Setup structure of documentation and added all placeholders for content to be completed.

Updated resources fields to match latest code.