Use direct inclusion, not submodules, to bring Javelin into Phabricator

Summary:
Submoduling is slightly convenient for developers but hellishly difficult for many users. Since we make about a dozen updates to Javelin per year, just include the source directly.

Even if we run `git submodule status` more often, this creates additional problems for users with PATH misconfigured.

Fixes T2062 by nuking it from orbit.

Test Plan: Loaded site, browsed around. Grepped for references to submodules.

Reviewers: btrahan, vrana

CC: aran

Maniphest Tasks: T2062

Differential Revision: https://secure.phabricator.com/D4581