Mondo Model class change: The collection names are now object methods

The collection names they are set at creation of the mango object can be
used as methode. E.G.:
my $mango = Mango->new(collections => [ 'document1' 'document2']);
$mango->document1->find({});
instead of $mango->find({}, 'document1');
Which is still valid.
Bugfix: changed some typos from mango to mongo :-)

and tested application