Add contextify.cc and use it for new vm.js.
Fix context-circular-references test to use getGlobal().

Contexts are no longer represented by their global object. This may be bad?
Fix spacing.
Wrap to 80 characters.

(Except for the error messages which will get re-done anyway.)
Use `ThrowError` for error messages.
Do not set return values when rethrowing.
Use `node_isolate` everywhere.
Fix casing of createDataWrapper.
Two newlines between all functions.
No need to return `this` from constructors.
No need for `Integer::New`.
No need to set anything if property not found.
No need for `Boolean::New`.
Fix missing newlines in the header.
Use `.As<String>()` instead of `->ToString()`.
Use `Context::Scope` instead of manual enter/exit.
Clean up `#include`s and `using`s.
Fix JS spacing.
Put files in the right place and in node.gyp.
Two space indent in tests.