Add vector LaTeX command (\vec)

The vector command places a right arrow above the text name of the vector.
This commit models the rendering of LaTeX where the arrow does not
extend to the full width of the vector name.
supervisor runs make instead of index.js

no need for verbose child_process code in index.js, just use make to
guarantee `make test` has run before the server is started up again
tiny handwritten static server instead of Connect

Connect isn't super heavyweight, but it and all its dependencies can be
replaced by this tiny thing

it's under script/, instead of having index.js polluting the top level
don't expose entire filesystem to the world

it's a not a huge deal since the server is only exposed to the local
network, and you can specify HOST=localhost to restrict to only your
computer, but still, it's pretty dumb to make it possible for anyone at
all to read your /etc/passwd with http://localhost:9292//etc/passwd

[path.normalize][] fixes this, collapsing multiple slashes and any
directory followed by ../, plus removing all leading /../'s (so no
http://localhost:9292/../../../../../etc/passwd funny business)

[path.normalize]: http://nodejs.org/api/path.html#path_path_normalize_p
log requests, like Connect's static file server

even better, because it has a timestamp on the request
if err, 404 or 500 instead of 200-ing a blank response
fix #190 $ at end of TextBlock causes errors later

2a4189c7be7162622d9c9b3b252c9c3f5d5b843f should've done this:
https://github.com/mathquill/mathquill/commit/2a4189c7be7162622d9c9b3b252c9c3f5d5b843f#L0R492
fix #152 renderLatex errors if selected to edge

after mutating this.ends, writeLatex disowns the selection, but the ends
of the selection are now malformed
Merge pull request #189 from mathquill/build.simplify-server

tiny handwritten static server instead of Connect
EtherPad discussion way, way out-of-date

and is being (unintentionally, by people who don't know how to use
Etherpad?) vandalized. It's been archived at the "v0.3 Architecture"
wiki page.
Cleanup based on @laughinghan feedback.

Remove redundant method name assignments.
Fix indentation (tab to spaces) in stylesheets.
Remove extraneous CSS properties from ruleset.
Merge pull request #185 from devlin/add_vector

Add \vec, using the Fraction technique of display:block and line-height
merge from upstream