added option to create account custom data along with account
Merge branch 'development' into custom_data
custom data implementation added
added custom data support to account
disable overriding of attributes that should be Resources, but can be called on create e.g. create custom_data along with account
allow deletion of specific resource values e.g. DELETE on account/1234567/customData/custom_data_field
improve materialized check logic

Instead of relying on only 'href' being set, we check that we
haven't materialized the resource explicitly. This helps with the
case where the user adds or changes properties locally without
first materializing the resource.
reimplement Custom Data resource

Make it behave like a Python dict, and simplify properties
serialization/deserialization.
remove the hardcoded special-case for deleting CustomData attrs
fix tests

They accidentially passed because check turned from desired:
    if "name" in ("name,):  # element-in-sequence check
to
    if "name" in "name":  # substring check

Which have the same result in the happy path (example here
uses "name" for the content of the key being checked in).
Merge pull request #1 from senko/custom_data

Custom data
fixed bug that incorrectly set the resource as materialized - dict.keys() is no longer a list in py3
latest httpretty breaks tests for py32 and py33 - again
fixed bug in tests - py3 doesn't rely on __cmp__ so it can't sort a list with dicts, integers and other lists automatically
moved custom_data import with other resource imports
ensure fetching of data if it isn't already fetched and override user set properties
just rely on _set_properties to do the right thing and set the materialized flag correctly
support for group custom_data added
uncommented tests marked FIXME since this works now, some pep8 fixes
deleting non materialized property causes an error but we should try to delete it on the server anyway