* removed accidentally added file
* In order to fix memory mismatch between runnable stages and what registered executors can run:
- clients are now stored using instances of he ExecClient class which stores the clientURI, running stage, timestamp and max.
- an array of memory requirements for runnable stages is kept at the server
- check in the server mainLoop that the minimum memory requirement is met by any of the active executors. If this doesn't hold, the server will die. This fixes #126
* updated the message "Not enough resources..." to specify whether this is due to memory or processors
* added a 1sec sleep before re-trying a stage to avoid i/o race conditions
* added memory information (stages and executors) to check_pipeline_status.py