Add bot usernames for twbs/bootstrap

[sagesharp]

Many github communities use bots to suggest reviewers, do automated testing, and more.

foss-heartbeat breaks bots into a separate category in the html contribution statistics, by checking for the username in getBots in ghstats.py.

Additionally, if a bot merges a commit after being issued a command in a pull request comment, appendReviewers in ghcategorize.py will attribute the merge to that person, as well as to the bot. Currently, we check for a specific command string at the beginning of the comment. If your test-and-merge bot accepts commands in the middle of a comment, please update the code.