Merge branch 'moriyoshi/7bit-and-8bit-transfer-encoding' into private-release
Bump version.
Do not supply charset parameter to set_payload.

It eventually instructs email.message.Message to dismiss the charset specified in Content-Type and furthermore recode the payload charset according to the global mappings predefined in the module, which is totally unwanted.
Merge branch 'moriyoshi/do-not-specify-charset-when-already-encoded' into moriyoshi/7bit-and-8bit-transfer-encoding
Bump version.