support String type INFO fields with multiple values

I have String type INFO fields with multiple values, but PyVCF currently does not split these by the comma char into multiple values, it returns a single string. I see that there is a special exception for String type INFO fields in the code handling multiple values, so maybe you have a good reason for doing this (some legacy VCFs that have commas in INFO fields where they shouldn't?) But the VCF 4.1 spec does state that comma is reserved in INFO fields values for specifying multiple values, so the current behaviour is not standard (and I have to add special cases in my VCF-handling code to work around).