Generates names and checks their availability on Twitter
Uses provided name as set of characters and generates all available subsets of that set.
Checks availability using HTTP status of URL http://twitter.com/<username>
.
If returns 404, the name is considered available.
Automatically rejects names shorter than 4.
-name="": base name used for generation
-sleep=500: sleep in ms between requests
-verbose=false: output all names, even taken ones
-workers=4: number of workers querying Twitter