Introduces a utility class for cleansing params.
Refined Hash instead of implementing a util class
Parameters will now be an extension of Hash

This will mean that using it is as simple as using a standard
Hash. It will automatically cleanse values at all points to prevent
values being stored in incorrect formats. It also means it can be
used in any situation that a Hash is used.
Finished Parameters class.

Parameters act identically to a Hash except they format input to
prepare it for use in the Sendgrid API.
Began using Parameters in API clients.

Switched from Hash to Parameters to ensure cleansed API params when
using Client or an extension of Client.
Fixed response#errors? and response#error_messages
Ensured nil parameters aren't stored
Version bump