* Refactor plugin to be compatible with Drone 0.5
* Add vendor files
* Re-add logo.svg, make loading environment from .env file optional, and use drone-go/template
* Fix README
* Fix issue with date formatting, update the DOCS, and improve types
* Add working directory and volume mount to README example
I have switched the mail sending mechanism to gomail to get more power
out of the sending method. Beside that I have added a flag to skip
certificate verification.
On top of that I have integrated the drone templating to make it
possible to overwrite the email templates optionally.
To be more compatible I have created a plaintext message format with the
help of html2text as well.
