allow running without Tornado
Merge pull request #139 from ulzha/master

allow running without Tornado
Add-fix tornado bug

Only load tornado dependent classes when tornado is available.
Merge pull request #140 from wouterdebie/master

Add-fix tornado bug
Rewrote README.md and added the examples from the PyData 2013 preso by Elias

RFC: let me know if this makes sense.

Updated pictures to use the new visualizer, except the big splashy dep graph which I'll do later.

Removed some crap in examples/ and doc/ and added some more random stuff to README.md
Merge pull request #143 from erikbern/new-doc

Rewrote README.md and added the examples from the PyData 2013 preso
Minor fixes in readme
Minor fix about triggering many tasks
Updating from main master
Fixing merge conflict