Remove extraneous call to `_.uniq`

This call served as a guard against a bug in the CSSselect library. That
bug has been fixed in the latest version of the library, so it may be
removed.
Rename `Cheerio#make` to document private status

`Cheerio.prototype.make` is a method intended for internal use only. It
is attached to the prototype for ease-of-use, as recommended by the
project's style guide. In order to prevent confusion, this method's name
should be prefixed with an underscore ("_") character.
Remove internal `connect` function

Most of this function's responsibilities concerned patching incorrect
behavior of the `htmlparser2` library. Since the parser has been fixed
in the latest release, that logic (along with the associated unit tests)
may safely be removed.
Merge pull request #331 from jugglinmike/remove-connect

Remove internal `connect` function
added nextUntil() and prevUntil()
minor code improvements and better tests for the filter parameter
removed extra whitespaces and improved test descriptions
code optimization by caching a couple of select operations
implemented DOM node and jQuery object selector types for nextUntil() and prevUntil()
small code optimization and fix for an issue caused by the switch to CSSselector
added support for filtering out non-element nodes