Replace mutable default parameters
Simplify chained comparison
Fix spelling mistakes
Fix PEP 8 coding style violations
Remove redundant parentheses
Fix instance attribute defined outside __init__
Fix single-quoted docstring
Small CSS fixes
Tweak .gitignore to ignore more coverage files
Minor cleanup of Python client
Add metadata extractor plugin
Merge pull request #316 from jamiesnape/metadata-extractor

Metadata extractor plugin and some minor fixes