Use entity number for plus sign in push emails
Was doing some testing today and found that both outlook and gmail had issues displaying the html content produced for push emails when a file was added.
This is how gmail shows it:
And this is for Outlook:
iOS devices work with the + entity, as does Mail on OS X, but I'm wondering if it is only available for newer html parsers (a quick browse on the w3c site seems to show that it was added in html 5).
Changing the entity to `+` and both gmail and outlook and iOS and Mail.
See merge request !721
