0.6.2: compatible with hhvm-autoload 3.0

Use an (untyped) Hack script as the binary (#38)

The README.md specifies that you should run the binary using hhvm.
The binary is actually a shell script.
This causes the following error:

The previous version gave this error and did not execute anything.
Fatal error: Uncaught Error: A semicolon (';') is expected here
 in /path/to/hh-apidoc/bin/hh-apidoc:2
Stack trace:
#0 {main}

I've cloned this style of binary from hhast.