ruby binding: add method Vector.raw_memcpy

This method allows to set vector values from ruby via FFI
pt = FFI::Pointer.new
vector.raw_memcpy(pt.address,size)

Example in the context of rock-robotics:
conversion from cv::Mat to frame::Frame
frame.image.raw_memcpy(mat.data.address,mat.total*self.pixel_size)
ruby_binding::vector_raw_memcpy: fix NUM2ULONG
ruby_binding::vector_raw_memcpy: add memcpy check
Merge pull request #2 from D-Alex/master

ruby binding: add method Vector.raw_memcpy