Update README.md

I don't know if this will eliminate confusion. I was accurate before I just assumed I knew what it was going to tell me.
The next line: "You can include `/js/boundarizr.js` (or .min.js if you prefer) and call `Boundarizr.testCurrentDocument()`."
is not related to the bookmarklet right? It's about adding it to a project?
Merge pull request #3 from getsetbro/patch-2

Update README.md
Add class name(s) to the boundary's label.

Since id usage for elements is less common than classes, the label for
the layout boundary is often “div”, which is not helpful. This change
will make the label similar to how the dev tools show elements
`div#id.class-one.class-two`

I also ran build.js to update the bookmarklet and minified file.
Merge pull request #5 from Vestride/add-classname

Add class name(s) to the boundary's label.
Merge remote-tracking branch 'upstream/master'
added support for changing tabs and navigating