Allow for `return' in solutions

Signed-off-by: Stephen Celis <stephen@stephencelis.com>
Merge remote-tracking branch 'stephencelis/method-solutions'
Fix: Update levels to use return true syntax

A recent comment has made it possible to prematurely return out of a
proc.  For some levels, this makes the code more readable as it does not
require storing the state of the solution in a variable and returning it
at the end.