Chai uses Object.create() so needs es5-sham to be loaded first on IE9.

Chai doesn't work for IE <=8, but this should get us (closer to) working
on IE >= 9.  Removed IE <= 8 from testling config, since we will never
pass tests there unless/until we rewrite the tests to use something other
than chai.
Merge pull request #159 from cscott/fix-ie9

Chai uses Object.create() so needs es5-sham to be loaded first on IE9.