array of locked config still can be modified

[Simon Duncombe]

require 'configatron'
 => true 
2.5.0 :002 > configatron.test = []
 => [] 
2.5.0 :003 > configatron.lock!
 => true 
2.5.0 :004 > configatron.test << 1 # should raise exception
 => [1] 
2.5.0 :005 > configatron.test
 => [1] 

I think subclassing of Array might be required to fix this.