Feature Request: Match with prefix only

[SleepyBag]

Say, I have following history:

python foobar.py
which python

And when I enter python and press c-p, which python matches my query. This is sometimes confusing.

So, could I have a option to match only with prefix? How do you think about this idea?

[h0adp0re]

This was also requested in #95 and a subsequent PR (#96) was filed. Consider merging your efforts.