Tentative support for compiler-filtered ES6 test HTML output.

Now, in addition to the normal es6/index.html, special versions whose tests have been pre-compiled with a given compiler. Currently 6to5, esnext and es6-transpiler are used. Polyfills are not yet inserted, nor is the output cleaned up compared to the normal table. Additionally, tests that use eval() or Function() will probably not work.
Fixed a slight bug with the compiled code.

To allow 6to5 to compile the test interiors, they are wrapped in an IIFE. But, this IIFE wasn't being II'd correctly.
Compiler test pages.

 * Compiler test pages are output in a compilers/ subdirectory.
 * Compiler test page output now uses a separate skeleton file.
 * Added Traceur.
 * Added polyfill injection.
Fixed a bug with the polyfill injection code.
Added TypeScript to the ES6 compilers list.

Unfortunately, the only way to invoke TS from Node is to use a lot of file IO.

This uses child_process.execSync, so it requires Node v0.11.12.
Merge pull request #309 from webbedspace/compiler-testing

ES6 compiler testing pages