Update acknowledgments to recognize GitHub

Signed-off-by: George K. Thiruvathukal <gkt@cs.luc.edu>
Update download links to go to GitHub instead of Bitbucket

Signed-off-by: George K. Thiruvathukal <gkt@cs.luc.edu>
Update additional references to go to GitHub instead of Bitbucket.

Signed-off-by: George K. Thiruvathukal <gkt@cs.luc.edu>