added fallback search argument

[jshaw]

added a fallback search argument for when you need to make sure that there's content in the tweeter feed section of the page. If there's no specific tweets with a hashtag it will default to a more generic search perhaps.

Works with caching and all of that stuff too.

[jshaw]

Also added twitter search term exclusions like for the get_tweets

[coagulant]

Please rebase your commits on top of current dev, so that Travis build can run properly (I've fixed coveralls dependency).