Change test suite to py.test.
Move test suite to webhelpers2.tests.
Convert single quotes to double quotes in tests.

Except for strings that contain embedded quotes; e.g., HTML attribute values.
Rename several dict helpers and change 'keys' arg.
Port 'containers' tests to py.test.
Port 'date' tests to py.test.
Port 'misc' tests to py.test.
Port 'number' tests to py.test.
Port 'text' tests to py.test.
Finish implementing 'urlify()' test.
Port 'html.builder' tests to py.test.
Port 'html.tags' tests to py.test.
Split multiple asserts to individual tests.
Port 'html.tags.ModelTags' tests to py.test.
Port 'webhelpers.html.tools' tests to py.test.
Port former 'html.converters' tests to py.test.
Add __init__.py to package.