Add options to grep

Refs #31.
Merge pull request #67 from andylolz/31-grep-opts

Add options to grep
Improve grep docs

Refs #31.
Add required args.

Need to implement some error catching.
More docs updates
Update head and tail docs
Update delete docs; tweak other docs
Stop streaming and respond once we’ve read enough.
Merge pull request #71 from andylolz/15-halt-stream

Stop streaming and respond once we’ve read enough.