Improved searching

Searching through questions is currently very primitive. It's simply implemented as:

```
for question in funcfinder.questions.functions.itervalues():
search_string = (question.__name__ + question.__doc__).lower()
if all(imap(search_string.__contains__, terms)):
```

There is no indexing to improve speed, fuzzy matching (i.e. users can't make spelling errors or use a synonym that wasn't explicitly inserted by the author), boolean operators, or any other features typically offered by search engines. What would be a good solution to improve search without diminishing the convenience of the `funcfinder find` command?