Revert "Update greaseshim.js"

This reverts commit 5b1252e41a6c3f87ede3222fc85caa32f787b159.
Revert "Revert "Update greaseshim.js""

This reverts commit d50351202a8e61545ba10c4d2f507041d8718959.
Add support for GM_xmlhttpRequest
Update README