When creating a `stream`, check for `class` before `filename` so classes can have the filename parameter
Add hooks to valid prefixes list for the set command
Enable reloading of modules
Merge branch 'allow_stream_class_with_filename' into enhanced_reload

Conflicts:
	circus/stream/__init__.py
Optimize for the FileStream case
Optimize loading of circus standard output types
Call close on streams if possible and allow replacing live streams
Reload workers if we had to create a redirector
FIx formatting
Merge pull request #676 from scottkmaxwell/enhanced_reload

Enhanced reload