add check for empty email subject
add spec for empty email subject check
update CHANGELOG
Add method for sender header
Display the sender header when specified
Merge pull request #60 from sjtipton/add-sender-header

Add sender header
update CHANGELOG
add links to each contributor

[ci skip]
Merge remote-tracking branch 'ryanb/master'
Edit the README in order to explain where and how to use this fork with the bundle command and the ability to use a git repository like the source