Add task for building custom version of jQuery

We use a custom build of jQuery that omits the modules that aren't
absolutely necessary for the snippet & typeahead. This commit adds a
make task that makes a shallow clone of the jQuery repo, checks out the
tag for the version we are using (v2.1.1) and runs the grunt task to
create our custom build.

After making the build, `sed` is used to cut off the last line before
copying it to the working directory. This is important for when we go to
create the bundle: the jQuery build process puts a source map
declaration at the end, which is a newline that starts with `//#`. When
we go to concatenate the files, this can mess things up.

This commit also does general cleanup and refactoring of the Makefile.
Remove "prototype" ribbon.

I'm going to start testing the snippet exactly as it will show up in
about:home so I removed the prototype ribbon.
Include the snippet HTML in the index.

This is part of starting to test the snippet as it will be implemented
on about:home. Learning a little more how things are implemented, it
probably makes sense to put the HTML directly in <div id="snippets">
rather than loading it from JavaScript.

A counter-argument to this would be that if for some reason the
JavaScript fails, it'd be better to show no snippet at all versus one
that doesn't work when the user tries to interact with it.

I'll have to consider this and maybe get a second opinion, but for now
I'm going to include the HTML directly on the page.