Add 'http://' to links in helloworld.md

Links to 'Assembly Troubleshooting on the wiki' and 'Fine Tuning' at the bottom of the 'helloworld.md' page were missing 'http://' at the beginning so they were trying to resolve to 

http://docs.shapeoko.com/www.shapeoko.com/wiki/index.php/Assembly_troubleshooting
http://docs.shapeoko.com/www.shapeoko.com/wiki/index.php/Tuning

which didn't work!
Merge pull request #19 from MakerCreative/gh-pages

Add 'http://' to links in helloworld.md