module Hashie::Extensions::SymbolizeKeys

def symbolize_keys!

test # => {:abc => 'def'}
test.symbolize_keys!
test = {'abc' => 'def'}
@example

Convert all keys in the hash to symbols. 
def symbolize_keys!
  keys.each do |k|
    symbolize_keys_recursively!(self[k])
    self[k.to_sym] = self.delete(k)
  end
  self
end