Use domain sockets to connect to R processes

This provides better performance and, more importantly, better security
versus the previous TCP socket implementation.
Add support for client sessions
Merge branch 'master' into domain-sockets

Conflicts:
	lib/proxy/http.js
	lib/worker/app-worker.js
	lib/worker/worker-registry.js
make sockjs work when shiny-server is behind a reverse proxy that uses SSL, according to https://github.com/sockjs/sockjs-client#deployment
Merge pull request #13 from planio-gmbh/master

make sockjs work when shiny-server is behind a reverse proxy that uses SSL
Move responsibility of handling worker acquisition to a "Scheduler."

Initially just implementing a simple scheduler that replicates the previous behaviour.
Use pkill and SIGABRT in a Mac environment so R is successfully killed.
Merged changes from osx-kill
Create placeholder for test.
Added agpl headers to the tests.
Added ability to direct traffic to a particular worker.
Merged poly-scheduler with master
Merged domain-sockets branch in.
Bumped to 0.4.0
Updated tests and fixed username bug.
Merge remote-tracking branch 'origin/master' into no-su
More work to remove root requirement

- Error on config load if insufficient permissions for config
- Dynamically choose whether to su in app-worker

See TODOs at top of config-router.js for remaining work.