Update test case to cover issue #1.

- Test cases covering the `useCanonical` method have been updated to
  ensure that the output parameter is being converted into a string
  representation of the boolean value.

This covers the bug in issue #1.
Fixed #1 - convert bool to string

The Wordnik API expects the `useCanonical` value to be either the string
`true` or the string `false`.
Improved fix for #1 - Convert bool to string

The API expects all boolean parameters to be represented in string form
(either `true` or `false`), therefore it only makes sense that all
parameter values being declare, which are boolean, be converted to string
form.
Merge pull request #2 from alanly/develop

Fixed #1 - Boolean parameters should be represented as strings.