Adds schema methods to Option and Config classes.

Adds a schema() method to Config and Options classes that returns their json schemas. Adds unit tests to test_config.py to test schema methods for Config and all Option types. Also adds a test_float file with FloatOption unit tests.

Related to: #632
The JSON schema spec doesn't actually include floats. Instead, it has 'number' for any numbers, both whole and fractional, and 'integer' for just integers. It's described here:
http://json-schema.org/latest/json-schema-core.html#anchor8