Fixed charset from configuraiton is ingored when calling htmlBody
Fixed invalid format content-type
Fixed hard coded charset. refs #66
Enabled supporting SKINNY_ENV environment variable
0.9.27-SNAPSHOT
Fixed SkinnyEnv.Key -> SkinnyEnv.PropertyKey
Fixed #65 for now (if really needed, others should be implemented)
version 0.9.27

 - Mailer: Fixed invalid Content-Type by @BlackPrincess
 - Mailer: Fixed #66 Fix hard code charset by @BlackPrincess
 - Mailer: Fixed #65 TODOs in RichMimeMessage
 - Enabled SKINNY_ENV environment variable
 - Renamed SkinnyEnv.Key to SkinnyEnv.PropertyKey
Merge branch 'release/0.9.27'