Required changes:
* Ignore ocaml.doc and ocaml.text attributes, which are now
  automatically extracted from comments.
* Swap type definition attribute syntax in test/* files.

Other changes:
* Add opam package file and `make init` command for dependencies.
* Change "Automatically Generated Attributes" documentation to comments.

Removes requirement for the compiler to be distributed with the
generator.
There is still a hard dependency on the precise OCaml version due to
syntactic changes between 4.02.1 and 4.02.2.

Also fix errors in type signatures in JsInterpreter.ml

This will permit us to run the test262 prelude in a separate context
from the testcase itself.
This was a bug in the original JSRef, see issue #9:
https://github.com/resource-reasoning/jscert_dev/issues/9