Try passing in an invalid username

Since basic auth uses a colon to separate username and password, a
colon in the username is not permitted, as it would confuse the
distinction. This is a test to see if clients are discouraged from
doing so. Sadly it seems CFHTTP… carries on regardless
Throw exception at invalid username
Chuck in some documentation
Merge branch 'tests' into invalid-username
Merge branch 'tests' into invalid-username
Merge branch 'master' into invalid-username
Merge pull request #3 from karelia/invalid-username

Code to deal with usernames that contain colon
Minor code cleanup from pull request
Modified readme and documentation
Updated podspec
Updated README