I know you are asking the question, why the f#ck would you want to move from #Github to #Bitbucket, however some clients just dont want to pay $7 a month for a private repo...
Moving right alone now...
Make sure you have a cloned version of the repo somewhere nice and local on your system...
$ git clone email@example.com:[user or org name]/[repo name].git #Remove the 
This will by default clone all the remote branches which can be found by:
$ git branch -r
Then you need to add local tracking branches for all your remote branches:
$git branch --track development origin/development #Repeat until all remote branches have local branches
Now go and create your new repo at Bitbucket. (You should be able to work this bit out... Im hoping)
Then add this as a remote in your local git repo, like so:
$ git remote add bitbucket firstname.lastname@example.org:[user or org name]/[repo name].git #Again remove the 
Now lets push all the branches to bitbucket:
$ git push --all bitbucket
Then all the tags:
$ git push --tags bitbucket
And finally rename the remotes, I alway like to just keep the point to github around like so:
$ git remote rename origin github
And the change Btibucket to origin:
$ git remote rename bitbucket origin
You should now have moved over your repo to bitbucket. :)
Let me know if I missed anything. Thanks!
P.S Be good to your mother!