Add AddressComponentType.POSTAL_CODE_PREFIX enum

[cowwoc]

#37 was closed but never fixed. Please add this enum value.

[cowwoc]

Both AddressComponentType and AddressType enums are affected. I am getting this warning:

18:17:44.728 [pool-1-thread-1] WARN  com.google.maps.internal.SafeEnumAdapter.read() - Unknown type for enum com.google.maps.model.AddressComponentType: 'postal_code_prefix'
18:17:44.730 [pool-1-thread-1] WARN  com.google.maps.internal.SafeEnumAdapter.read() - Unknown type for enum com.google.maps.model.AddressType: 'postal_code_prefix'

[cowwoc]

Can you please publish a release with this new enum? My code needs to skip over postal code prefixes but I can't do so until this enum value is added. (Is there a workaround?)

[markmcd]

We're currently discussing some options for how best to implement this (in #49) but in the meantime, feel free to send a pull request through and we'll take a look.