Prepare to release 0.0.4
Makefile: upload: Don't fail if pkg/*.gem not exist
Add Net::SMB#xattr, Net::SMB::Dir#xattr, Net::SMB::File#xattr
Net::SMB: Cache rb_intern("call")
rb_sys_fail(url) instead of rb_sys_fail("SMBC_*_ctx() failed")
Net::SMB::File#seek: Raise correct exception