Friendly file limit error

[ollieglass]

As suggested here #22

[coveralls]

Coverage decreased (-1.7%) to 97.49% when pulling aaad1ef on ollieglass:friendly_file_limit_error into 36f909d on ajtulloch:master.

[mwojcikowski]

I don't like the use of bit.ly, It would be much useful if we had an information about this in the README.

I've got an idea, that we could predict obvious failures, i.e. when the limit is below the predicted usage, issue a warning message and/or try to increase the limit within the script via resource module.

[mwojcikowski]

Plus, such error can come up on every NamedTemporaryFile not only in one place. I'm against wrapping all of them up in try: except. The best solution would be, in my mind, simple check for the resource limit and issue a warning that things will break.

I don't agree that these errors are dubious in any way for Linux/Mac.