Strip basic quoting from email subjects - resolves #14

This adds some simple logic to check for basic quoting of the email subject, and strip it out if it's being used.  RFC2047 quoting using `=?charset?encoding?encoded-text?=` won't be affected, but simple quoting using " characters will be stripped from email subjects.

It solved my issues related to #14, and AFAIK shouldn't change anything else.