Capstone 4.0 support

[david942j]

Capstone 4.0 has released and Crabstone raises an error when facing capstone 4.0:

RuntimeError: FATAL: Binding for 3.0, found 4.0

[david942j]

Related issue: capstone-engine/capstone#1315
And this repo seems not being updated since 2015, If @bnagy need a new maintainer of crabstone, I'm glad to be the one.

[david942j]

For anyone needs Capstone4 support and comes to this issue -
my fork of Crabstone has been upgraded to support Capstone4, and the gem has been pushed as well.