fix bug in mismatch method of AnswerShow
add input to user search form for Order By
correctly display users randomly, with placeholder (min_age) for order by match_pct
refactor User#users to order by match_percentage when specified
don't fetch twice to find match_pct when indexing users
restyle users index
fix bug in User#users where 'and' is repeated in where_str
have User#users show users with no question overlaps as having 0% match (for some reason specs no longer work)
begin to debug displaying profile questions for users who haven't answered certain questions