Create hyperlinks for URLs in plaintext emails

[GREsau]

This will change all URLs found in plaintext emails to hyperlinks. The links should open in a new tab, like they currently do with HTML emails.

The regexp to find URLs is fairly dumb, but it seems to do the job - for each occurrence of http:// or https://, it just keeps going until it finds a character that is not valid in a URL (e.g. whitespace).

I didn't commit the updated assets.go, since I'm using Windows which messed with the line-endings and file permissions (which I'm 98% sure doesn't actually matter, but I'm erring on the side of caution).

[GREsau]

A quick before/after comparison with a test email:


Not much to see, just a couple of hyperlinks.

Also, the failed travis CI build looks unrelated to my actual changes. I'm not sure why the uuid package is even in the makefile, so I'll leave it for someone else to investigate.

[ian-kent]

thanks @GREsau