Added ability to query slaves for executors.

  - can pull list of executor objects for
    each slave
  - added unit tests for new code.
Added systests for executor feature. Other fixes.

 - fixed missing index in executor.
 - removed unnecessary try/except block in executors
Randomize jenkins http port for systests to avoid collision with default 8080
Adding myself as a contributor
Merge pull request #191 from makewhatis/executor_module

Added ability to query slaves for executors.
Merge pull request #194 from adamreid/master

Randomize jenkins http port for systests #181