Add spec for wait methods

This is a migration of the watir-webdriver wait_spec with the following
changes:

1. The error message checking in the Watir.default_time specs was
removed. The error messages are already checked in the specs for the
specific wait methods.
2. Added deviations for watir-classic on error messages that include
element locators. Watir-classic currently includes :tag_name as an array
rather than a string.
Merge pull request #40 from jkotests/Add-wait_spec

Add spec for wait methods