* Make webworker-threads an optional dependency.

  If WebWorker Threads is unavailable, use vm.createContext
  as a same-thread fallback as before.

  Initial micro-benchmark shows that threads offer 2x throughput
  even when concurrency=1.
* Fix typo in package.ls
* Support for rolspan/colspan/title in HTML export.

  Closes #24; @spaceshipoperator++
* Compatibility with webworker-threads
Added cmdline switches: -v to force vm.createContext , -w for webworker-threads (which is default)
removed leftovers from implementing cmdline switches (-w for webworkers -v for createContext)
Merge pull request #27 from abiank/master

implemented cmdline switches in sc.js
* Change `-v` to `--vm` and document its usage.
* Remove debug statement
* Add "make vm" target to run with --vm.

  Also rebuild SocialCalcModule.js as part of "make".
* Repair /_/:page/cells and /_/:page/cells/:cell.

  Closes #28. Reported by @allesandro++.
* Release 0.20121230.0
* Rewrite ((_, x)->..) as ((, x)->...) as per @Nami-Doc.
* JSON has "null" not "undefined"
* Fix #26 and #32 by defaulting text to table-layout: fixed.
* Release 0.20130116.0
* Add HEXCODE() for @favonia
* First sketch at horizontal scaling
* Only connect to Redis for socket.io if we indeed have a redis server.
* Note that horizontal scaling relies on Redis