added font-family to body and font-weights to headers
create class styles for ease of text movement
move font-family to come after font-size
Merge branch 'master' into update-stylesheet

Conflicts:
	stylesheets/index.css

Used `git checkout --ours -- stylesheets/index.css`
and also added Helvetica as a fallback font-family which
was a change from master
Merge pull request #3 from githubstudent/update-stylesheet

Update stylesheet