Split form fields into canonical and index types

Require callers to be explicit about whether they'd like to coerce
form input with the `from_index` or `from_canonical` methods.
(`CanonicalEnumField` exactly replicates the current `EnumField`
functionality, but drops support for old-style dict-based enums.)
Configure pylint to ignore generated members

Pylint can't handle much dynamic-language magic, so configure it to
ignore known okay class attributes (Django's `objects` manager, our
enums' `index` and `canonical_name` properties, etc.).
Make type laxity of models.EnumField optional

Rename the current models.EnumField to models.LaxIndexEnumField, and
create a models.IndexEnumField that doesn't allow casting back and forth
to canonical names. Add more tests for both.
Merge pull request #11 from akshayjshah/split_fields

Split form and model fields into string- and int-based versions
Docs for form fields.
Adding CanonicalNameEnumField.
Merge pull request #12 from dhui/canonical

Adding CanonicalNameEnumField
Updating README.
Merge pull request #13 from dhui/readme

Updating README
Bump version of django-richenum
Merge pull request #15 from adepue/master

Bump version of django-richenum
Adds introspection rules for South
Merge pull request #16 from bennylope/south

Adds introspection rules for South
Add Ben Lopatin as an author.
Bump version number from 1.0.0 to 1.0.1
Merge pull request #17 from dhui/version

Bump version number
Update readme.
Merge pull request #19 from dhui/readme

Update readme.
_BaseEnumField: Make run_validators method a no-op

See the comment in this commit-- I can't see value in allowing custom
validators on EnumFields and the implementation in the superclass causes
warnings in RichEnum.__eq__.

Arguably those warnings aren't useful (warning against []/falsy compare).
In that case, we can revert this when they're silenced.

Alternatively, if we need the warnings and need this functionality, we'd have
re-implement the method in the superclass without said check, or live with
warnings every time a form containing an EnumField is validated, which sucks.
Update CHANGELOG and package version