Implement "symbolize_keys" method

[vovayartsev]

In v2.0.8 gem, 'symbolize_keys' method neither works nor raises any exceptions, which can lead to unexpected results, e.g.:

Settings.smtp_settings                  # => {"address"=>"smtp.sendgrid.net", "port"=>"587", .....
Settings.smtp_settings.symbolize_keys   # => {"address"=>"smtp.sendgrid.net", "port"=>"587", .....

It would be better if symbolize_keys method worked just like in Hash class

[alex-kovshovik]

+1

[goosetav]

I had the exact same use case as @vovayartsev

[atipugin]

+1 for this!

[ddonia]

+1