fixed; aggregation exec w/o callback

now returns a promise
fixed; aggregation exec w/o model

now returns a promise
tests; fixes for legacy node version
inital work on toConstructor in mongoose, needs tests
toConstructor() working and tests written

passing all tests. Additional fixes for dealing with `sort` passed via
`setOptions` Moral of the story: the storage format for sort sucks
Updated mquery version, removed sort hacks

Updated to new mquery version which gets rid of the terrible internal
sort syntax.
Fixed call signature of custom query call to super

Hadn't switched it from the old Query constructor syntax