Make sure tap search results are lower case
Better handling of tapped formulae search results

Previously, tapped formulae were included within the local 'names' search,
giving no indication that the result was from a tap, and not from core.
This is changed now.  For example, if you have tapped 'homebrew/python', a
search for 'numpy' will return 'homebrew/python/numpy' and no longer just
'numpy'.