Cleanup feature without Ruby code

[hsbt]

I added the feature of cleanup files without Ruby code. I removed the following files.

• The vulnerable files detected by F-Secure Anti-Virus.
• The files what used extension name without .rb, .rake and the majority of Ruby code.
• The files that ruby -c raised error status.

I know this feature is slow down of rake unpack task.

@akr @mame How about this?

[akr]

Is it remove C files?

[hsbt]

Is it remove C files?

Maybe, Yes. But I know we hope to search for C function usage like rb_*. Should we store files that are .c, .h, .cpp and .hpp ?

[hsbt]

@akr I also ignored C/C++ source files. Can I merge this?