Added "assign-node" to the job definition.

Added support for "Restrict where this project can be run" option in job configuration:
![screen shot 2014-10-17 at 16 16 13](https://cloud.githubusercontent.com/assets/9081245/4678554/b4d24af0-55f7-11e4-9bf8-68ee22045e4c.png)

Also small mistake corrected in documentation. Right command to build documentation is "tox -e docs". Old command "tox -e doc" prints "ERROR: unknown environment 'doc'."