Ensure credentials set in Twitter.configure are of a valid type.
This commit adds basic credential validation after the credentials are set using the Twitter.configure block. If the credentials are not a string or symbol, a Twitter::Error::ConfigurationError is raised with a helpful message.
Bug fix for iterating over friends or followers of someone else than the authenticated user
The developers of pry-nav recommend switching to pry-debugger on MRI 1.9.2 or greater.