Append exports to end of .bash_profile instead of overwriting
Append exports to end of .bash_profile instead of overwriting

In the process at an explanation of where the lines came from
so that users know they can remove the lines if desired.

selimnairb/2014-02-25-swctest,selimnairb/2014-02-25-swctest,selimnairb/2014-02-25-swctest,selimnairb/2014-02-25-swctest,wking/swc-windows-installer,ethanwhite/windows-installer,selimnairb/2014-02-25-swctest,swcarpentry/windows-installer,selimnairb/2014-02-25-swctest