Fixed PDoc for toQueryString()
`toQueryPair()`: `value` is already defined
Merged nested if() into single expression
Issue #1431: writeAttribute('checked') fails to write the 'checked' attribute, writes an 'undefined' attribute instead
Merge pull request #80 from sdumitriu/issue-1431

Fix an issue where `writeAttribute` tries to set an attribute named `undefined` in certain cases. [#1431 state:resolved]
Merge pull request #78 from victor-homyakov/patch-27

Merged nested if() into single expression
Merge pull request #77 from victor-homyakov/patch-26

`toQueryPair()`: `value` is already defined
Merge pull request #74 from victor-homyakov/patch-24

Fix PDoc for `toQueryString`.
viewportOffset: extend forElement (it's used twice)

`forElement` was used twice in `viewportOffset`:
1. at line 1147 as `var element = $(forElement);`
2. at line 1156 as `element = forElement;`
This leads to error when `forElement` is string: `Element.viewportOffset('id')`
Merge pull request #87 from victor-homyakov/patch-31

Prevent error in `Element.viewportOffset` when string is passed as first argument.
Possibility to remove X-* headers for CORS request

`setRequestHeaders()` unconditionally adds specific headers to any request.

This patch gives possibility to remove these headers in order to allow simple CORS request.

Based on http://stackoverflow.com/questions/13814739/prototype-ajax-request-being-sent-as-options-rather-than-get-results-in-501-err and https://prototype.lighthouseapp.com/projects/8886/tickets/1590-ability-to-remove-headers-in-ajaxrequestsetrequestheaders-for-cors
Merge pull request #88 from victor-homyakov/patch-32

Don’t send Ajax headers whose values are `null`.

This allows end users to opt out of `X-Requested-With` and `X-Prototype-Version` by explicitly setting them to `null`. (Use case: making a CORS Ajax request without a preflight request.)
IE8 fix for the opacity check

IE8 fails to set the match variable which throws a javascript variable
Merge pull request #90 from jwestbrook/IE8Opacityfix

Prevent exception in IE when calling `Element.getOpacity`.
Firefox 18+ supports String#startsWith, String#endsWith
Optional position argument

Added optional position argument to `String#startsWith`, `String#endsWith`, as described in https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/String/startsWith and https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/String/endsWith.
Documented new arguments and examples.
Updated unit tests
Bugfix in toQueryParams (didn't decode '+' correctly)
Add documentation example for `Element#clone.`
Merge pull request #96 from victor-homyakov/patch-33

Use native `String#startsWith` and `String#endsWith` if present. Turn existing implementation into a true polyfill.