Prohibit module initialization

[st0012]

This fixes #679. The solution is more complicated than just forbidden the method. I choose to let it work more like Ruby:

1. Class < Module and Module < Object
2. Module class doesn't support #new (but support .new)
3. Class class support #new

Before today our inheritance chain for Class class is Class < Object, so I changed it as described above.

@hachi8833 can you help me compare the Goby's behavior with Ruby again?

[codecov]

Codecov Report

Merging #681 into master will increase coverage by 0.05%.
The diff coverage is 94.68%.

@@            Coverage Diff             @@
##           master     #681      +/-   ##
==========================================
+ Coverage   81.94%   81.99%   +0.05%     
==========================================
  Files          57       57              
  Lines        7764     7798      +34     
==========================================
+ Hits         6362     6394      +32     
- Misses       1132     1133       +1     
- Partials      270      271       +1

Impacted Files	Coverage Δ
vm/boolean.go	92.3% <100%> (ø)	⬆️
vm/hash.go	97.02% <100%> (ø)	⬆️
vm/http_client.go	59.63% <100%> (ø)	⬆️
vm/string.go	95.81% <100%> (ø)	⬆️
vm/range.go	89.89% <100%> (ø)	⬆️
vm/simple_server.go	68.21% <100%> (ø)	⬆️
vm/concurrent_rw_lock.go	92.4% <100%> (ø)	⬆️
vm/null.go	88.23% <100%> (ø)	⬆️
vm/http.go	87.15% <100%> (ø)	⬆️
vm/integer.go	73.91% <100%> (ø)	⬆️
... and 20 more

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[st0012]

@hachi8833 can you review and approve it if looks ok?

[hachi8833]

Thank you for the implementation!

I checked the updated behaviors with Ruby's ones:

• Class inherits Modules
• Module inherits Object
• Inheriting modules on classes: prohibited
• inheriting classes on modules: prohibited
• performing #new on modules: prohibited
• performing Module.new: permitted
• performing Class.new: permitted

I think this can be merged.