Model before_update callback was not defined.
Index hash_key values were empty because of the key used.
Hash keys are converted to_sym.
Update persistent to use update callbacks.
Update .gitigore for RubyMine.
Merge remote-tracking branch 'origin/master' into before_update_fix

Conflicts:
	lib/dynamoid/persistence.rb
Merge pull request #123 from stefanneculai/before_update_fix

Model update callbacks were not defined.
Merge pull request #124 from stefanneculai/fix_index_hash_key

Symbolize keys passed to Chain#where()