Open .eml instead of download

[michi-zuri]

Most Chrome based browsers are able to display .eml files properly, including those with html markup. The current state of viewing a message doesn't handle html messages, just displaying all the css inline.

Currently, there is no easy way to open the .eml file in a new tab. Clicking on the download button just downloads the .eml file. Since my .eml files are already on my disk, there is no point in re-downloading them. After all, this tool is supposed to be used locally and not over the interweb. So instead of downloading I would rather have the message open in a new tab.

Would this be easy to implement? I'm happy to give it a hack and make a pull request if my feature request makes sense to you.