Do a `make clean` on a fresh vagrant provision.

While not necessary for fresh installs, this is done to prevent errors
that can arise if you are switching from running on your own machine to
vagrant. Make a note of this in the readme.
Decrease duration of notifications and fade out notification on click.

Quick fix for #2273 to improve usability until a long-term solution is
agreed on and implemented.
Merge pull request #2279 from juliepagano/master

Decrease duration of notifications and fade out notification on click.
Bump version to 12.4.3
Bump version to 12.4.3-dev
Merge pull request #2280 from aisipos/vagrant_clean

Do a `make clean` on a fresh vagrant provision.
Append index to schema.sql; #1417
Merge branches 'lil-branch-sql-doc' and 'master'
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.