Add slug method for the Internet module

The slug method takes two arguments, words and glue which determine length and character to join on. This code was taken from the original faker repository.
Add test for slug method in Internet module
Fix assertion for all glue characters, not just hyphen
Add slug to InternetSE and support for ruby 1.8.7
Add uncommitted comment
Use k helper instead of the respond_to for choice/sample
Merge pull request #131 from ethier/master

Add slug method for Internet module and associated test