Additional built-in scorers once pluggable mechanism is implemented

[bskinn]

Once #207 is done, or even perhaps in tandem with that implementation, could add some additional built-in scorers:

• contains: 100 if X in RST else 0
• regex: 100 if re.search(PATTERN, RST) else 0

These would be pretty straightforward to implement by a user via API, but might be good to have at CLI.

Of course, on POSIX both of these can be achieved with grep.

...

Well now. findstr on cmd, and Select-String on PowerShell.

Not. Needed.