Newer style retweets are summarily removed regardless of options.
Older style retweets (aka manual retweets) are tweets of the form
RT @user blah blah. If strip_manual is TRUE, tweets
containing the RT string will have everything including and to the
right of the RT will be removed. Everything to the left of the
RT will remain, as this should be original content.
If strip_mt is TRUE, tweets will be stripped in the same
manner as strip_manual but using the string MT
Value
A list of status objects with retweeted content removed