Merge pull request DusanKasan#19 from k-yomo/support-html-in-multipar…

…t-mixed

Add support for html in multipart/mixed

test brought in line with the others

Merge pull request DusanKasan#15 from xgess/xgess/fix-gomod

fix go.mod to this repo

Merge branch 'EdwinLove-seven-bit-attachment'