Typos corrected.

Mostly minor typos and grammar tweaks.

At one point make it clearer that "center" refers to the function.
Comment on allowable filenames.

The standard novice problem I see is putting spaces in filenames; this very briefly comments on what filenames are allowable without explaining why, as I assume there won't be time to cover that.
Merge pull request #2 from IanHawke/matlab-function-name

Comment on allowable filenames.
Merge pull request #1 from IanHawke/matlab-typos

Typos corrected.
Merge branch 'gh-pages' of github.com:swcarpentry/matlab-novice-inflammation into gh-pages