Patch beanstalkd collector

'version', 'id', and 'hostname' are not statistics and can be ignored.

See the protocol for a full list of outputs, and their description:

https://github.com/kr/beanstalkd/blob/master/doc/protocol.txt
Merge pull request #659 from MichaelDoyle/patch_beanstalkd_collector

Patch beanstalkd collector
Made pid detection more robust against invalid data (blank, non-numeric)
Merge pull request #662 from rogerhub/master

Made pid detection more robust against invalid data (blank, non-numeric)
PEP8: Fix comment style for PEP8 compliance
Merge pull request #671 from yuvipanda/minor-pep8-linting

PEP8: Fix comment style for PEP8 compliance