This change expands the locale parse to have the following properties:
- if only the language code is given, choses the regionalization that
occurs first in the locale list (e.g., "en" --> "en-US"
- if regionalization for the language is *not* present, choses the
generalized language or a different regionalization (e.g. "pt-PT" -->
"pt-BR")
- parses both the subject and body looking for the most specific
regionalization
- defaults to en-US if no available language is found