set x-forwarded-* headers in 'meteor run'

This was a regression in 0.6.6 when we upgraded to a new unreleased
version of http-proxy which now requires an explicit option to set them.
See #1624.
wait for server to be running instead of naive sleep.
added meta description
Handle long-polling sockets when we are shutting down the server with SIGHUP better
Short socket timeout while no pending request.  Long timeout with pending req
glasser comments
rename event with a meteor prefix
Upgrade websocket-driver from 0.3.0 to 0.3.1

This fixes a DoS we found:
https://github.com/faye/faye-websocket-node/issues/26
Add comment referencing #1648
Stop using handlebars in the bundler.

The dev bundle contains a copy of the handlebars NPM module solely for
creating app.html.  This is separate from the NPM module used by the
handlebars NPM package.

On the shark branch, we no longer use the handlebars NPM module for
Meteor template (it is being replaced by Spacebars), so in preparation
for that, we'll remove this barely-used build-time dependency on
handlebars.

A subsequent commit will remove it from the dev bundle.

Once the Spacebars API has fully settled (eg, it has been merged to
devel), we should get rid of this ad hoc templating and replace it with
Spacebars, either in webapp_server (driven entirely by program.json) or
by using unipackage.load in bundler.
Drop handlebars from the dev bundle.
Clean up package dirs containing only ".build"

These directories are often left around when switching from another
branch; git does not delete the gitignored .build directory (but it will
show up annoyingly in 'git status').
Drop uglify dependency from handlebars module

This reduces the npm download done when updating the handlebars package
by 2M.  (Uglify is only used by bin/handlebars, not the handlebars API.)
Add cursorSupportedByOplogTailing.
In "meteor run", run mongo in repl-set mode, so that oplog is available.

Note: this is pretty slow. Before merging this branch, should cache the fact
that replset has been initiated on port N so that on the next run, if the port
hasn't changed, we don't need to re-initiate.
Factor tailing code out of observe-changes code.
Don't reset the replset unless the port changes.

(Resetting the replset is slow!)
oplog checkpoint from friday
checkpoint monday morning
remove processing works.