Merge pull request #18 from mkeung/master

update links, update wallet to remove 'dig'
updated mac wallet images
Merge branch 'master' of https://github.com/kbouwser/howtodogecoin
added currency dropdown; added USD to doge guide; updated nav menu for all pages; updated error page
added imgur tipping section; updated nav menu
update footers with twitter and fb page links
Merge remote-tracking branch 'kbouw/master'
update menu label, footers for new pages