tutorials and screencasts pages: remove space before colon for legibility and remove broken link to username

There aren't public user pages to link to, so I removed the link altogether.
fix missing space and add test fixtures
Merge pull request #40 from kenliu/fix-tutorials-screencasts-colon-space-and-broken-links

tutorials and screencasts pages: remove space before colon for legibility and remove broken link to username