Replies and retweets

[antgiant]

I've added some functionality, but I 'm not sure if this is a direction you are interested in your bot going or if you would rather me just keep this a separate fork. This pull request makes three changes

1. Word filter can be disabled. (I was having extremely high false positives with it.)
2. Scheduled Tweets can now retweet (with or without comments)
3. Scheduled Tweets can now be replies to tweets.

Technically it wouldn't be to difficult to add points 2 & 3 to the other options like Every, Markov, etc. but I personally didn't see much value there so I didn't.

My much longer term plans include allowing multiple twitter accounts to be managed from a single Google Sheet but that will be a pretty massive change, so I am also interested in knowing if you would like that functionally contributed back into this or not. As your input would probably change how I architect the implementation of that.