format function arguments

[meetar]

Re: e.g. setDataSource(_string_ name, _object_ config), from https://github.com/tangrams/tangram-docs/pull/77#discussion_r59905348:

I think I actually took these data types out (string, etc.) awhile ago, because while they are useful to have somewhere, they were not being formatted correctly in the doc generation (where they show up in the left-hand nav), and are also not consistent throughout these pages. So we should find a standard that works.