Rename the `memberships` table to `takes`; #2282

`memberships` was a bad name for this table because it's ambiguous with
community memberships. Renaming to `takes` fits the usage we've arrived
at and is parallel to `tips`. Tips and takes! Membership is then an
emergent property of data recorded in the takes table.
minor change (make code more DRY)
add test for MixinTeam.get_members()
fix bug in MixinTeam.get_members()
Adding NFS support to supported platforms
Adding vagrant to the doc links
Moving initial data over to the account tab
fix extraction of avatar URLs from bitbucket API responses
Add note about using Vagrant on Ubuntu systems.
Merge pull request #2321 from gittip/vagrant-nfs-support

Adding NFS support to supported platforms
Clean up Vagrantfile.

blah
Move Vagrantfile back to root.
Move create db scripts into scripts dir.
update avatar after connect/merge and disconnect
Switching account tab to col0 and moving bank account information
Useless checking
no it doesn't
reformat & restructure the worst parts of account.js
cleanup
there's no need to empty the session header

don’t set it, and it won’t be there