Don't error if there's no member_info. Fixes #143

MPs that haven't been in parliament for a while some times don't have
it, e.g. http://localhost:3000/mp.php?mpc=Sydney
Don't show positions if we're displaying more than one member
Only add electorate to the search conditions if we know it
Show the summary view if it's explicitly asked for
Offices sentence should say "and" for last position
Match sort order of PHP app
Oxford comma the shit out of this because it's right

It's just a coincidence that it matches Rails <coughs>
Extract hack into helper
Display real start date if MP entered after our records start