Use a mirror of the PhantomJS binaries.

The rational behind this change is to insulate the NPM package from
removal of old binaries from PhantomJS hosting on Google Code. See
issue #22 for details of breakage.
Merge pull request #23 from Obvious/pupius-mirror

Use a mirror of the PhantomJS binaries.
Revert "Use a mirror of the PhantomJS binaries."

This reverts commit b1543e4473d07d31be149e277869d05cbb5e521d.

It is not necessary.
Bump version to 1.8.1-3 following revert of mirror change