Remove extraneous API options

In 0.1.0, inspect exposed the functionality to add your own
formatting methods. 0.2.0 adds support for a single option:
`color`. When `inspect.color` is `true` (default in Node.js),
inspect returns diagrams with ANSII-sequences. Otherwise, just
a plain diagram is returned.
Update changelog for 0.2.0
0.2.0