Fix readme
Fix wrong import and exception
Initial catalog and resize simulation

The catalog serves the image divided in 256MB chunks. For each chunk,
the download time is calculated with the following formula:

    time = chunk_size / (variation * bandwith / number of downloads)

The resize is simulated with the following formula:

    time = size / (variation * disk bandwitdh)
Start using oslo.config and CONF objects
Refactor usage of simpy environment
Move print_ function to utils module
Move catalog to its own module
Move fakes.py into scheduler.py
Remove global JOB_STORE
PEP8 changes
Move load_requests to utils.py
Add 'max_simulation_time' option