Prominent email button

[opatut]

Separated out of #64 for discussion.

[opatut]

@tobst You originally requested this. Please specify:

• Should the email button be a mailto: link? If so, expect some more spam on the linked address. If it's a Google account, that spam filter is probably good enough, but nonetheless -- it's a decision that has to be made.
• Where should the button go?
• What email address should be linked?
• Should the button also pre-configure a subject line in the mail client? This is possible with a href like mailto:foo@example.com?subject=Hello%20World, in most email clients (e.g. Thunderbird does support it).

[boldt]

Ich habe sehr gute Erfahrung mit spamspan gemacht. Diverse Mail-Adressen, welche damit auf Webseiten veröffentlicht sind, sind de-facto Spam-frei.

Vlt. bekommt man das ja auch in Hugo integriert.