fix typo

Introduce concept of "build version" to unipackages.

We bump the "build version" of the tools precisely when we want to rebuild all
packages.  This handles the "I ran meteor update, I may need to rebuild my
app/$PACKAGE_DIRS packages" case, as well as ensuring that warehouse package
version numbers are incremented when we need to rebuild all packages (but not on
EVERY tools directory change).

bump throttle timeout, see if it improves test run times

Update docs to 0.6.4-rc1.

Update docs to 0.6.4-rc1.

History.md updates.

Remove fixed width constraint. Fixes meteor#1043.

Update node mongodb driver. New version reconnects to mongo better wh…

…en there is a new primary.

Passes package and tools tests plus basic app sanity testing, but I have not done and deep or specific testing.

Tweak package descriptions.

Tweak package descriptions.