I noticed that some files in rubygems were executable, and I could think
of no reason why they should be.
In general, I think ruby files should never have the executable bit set
unless they include a shebang, so I run the following command over the
whole repo:
```bash
find . -name '*.rb' -type f -executable -exec bash -c 'grep -L "^#!" $1 || chmod -x $1' _ {} \;
```
This makes method_missing take a flag for whether keyword arguments
were passed.
Adds tests both for rb_call_super_kw usage as well as general usage
of super calling method_missing in Ruby methods.
