Second argument to `attr/prop/data` is always a setter

This enables setting `undefined` value
Improve tests that verify attr/prop/data setter erasing
Shorten checking if 2nd argument was passed

Continues on 761201e80fa81750d3cefe3d4d3cd2801b33362b
Setting maxLength to undefined yields weird result on Phantom

Apparently it sets maxLength to "524288":
https://travis-ci.org/madrobby/zepto/builds/29254260

Use a custom property to avoid magic browser behavior around certain
properties.
Merge branch 'attr-setter'

Closes #952, fixes #942
`$.proxy` now accepts additional arguments

Example:

  var fn = $.proxy(myFunction, contextObject, argument1, argument2)

Fixes #882
Fix `$.proxy` combining additional args with actual args
Merge branch 'proxy-args'

Closes #895
Use cache-busting for `jsonp/script` dataType by default

This is for jQuery compatibility.

Fixes #976
Fix `$.contains` on browsers that don't support native `contains()`

This fixes `$.contains` and functionality that depends on it on
Firefox 4.0 – 8.0.

Fixes #963
Avoid double blank line betwen intro and code in `dist/zepto.js`

Closes #923
Zepto.js 1.1.4
Moved variable 'type' declaration to outer function scope.

Doing this against my conviction in order to settle #980. Would much
prefer to move variables to the inner-most scope instead.
Merge pull request #980 from cederberg/patch-1

Moved variable 'el' declaration into inner scope
Include reference to Zepto Builder
Merge pull request #989 from galymax/patch-1

Include reference to Zepto Builder
Merge pull request #2 from madrobby/master

merge latest version