stub senders
remove the simple sender
fix merge re: removal of postmark sender
rudimentary postmark sending working
rudimentary postmark sending working
rudimentary postmark sending working
improved postmark sending
mandrill rudimentary sender operational
tests added, still need to handle mandrill multipart emails
removing coverage
mandrill handling multipart emails and attachments, tests passing
tests standardized, more fields added to mandrill
basic mailgun and sendgrid implementation. Need to standardize tests across platforms
simple sender
standardized return values for senders
refining readme
refining readme
refining readme
refining readme
refining readme