Escape the Subject: header using RFC2047

Incorporates the encoding code from rfc2047.erl from Zotonic to encode
the Subject: header.
Add parser for RFC 822-style address lists; encode all header values with RFC2047.
Add test with decode_header
Only report that gen_smtp is listening when it actually is doing that.
Move trap_exit to the beginning of the init call.
Merge pull request #35 from mmzeeman/init_error_logger

Don't tell error_logger that gen_smtp_server is listening when it is not.
Merge pull request #30 from zotonic/zotonic-subject-encoding

Escape the Subject: header using RFC2047
Handle lowercase base64 prompts for SMTP AUTH. Fixes #37
Fix long email address test