Fix the inherited instance variables

The missing colon meant that the inherited_instance_variables hash contained {nil => nil}, this was causing problems in other plugins.
Added binstubs to gitignore
Merge branch 'fix-inherited-instance-variables' of github.com:crofty/sequel_secure_password

* 'fix-inherited-instance-variables' of github.com:crofty/sequel_secure_password:
  Fix the inherited instance variables

Signed-off-by: Mateusz Lenik <mlen@mlen.pl>
Prepared release 0.2.5