dqrng 0.2.0

• Add R side support for selecting multiple streams for parallel usage.
• Implement long_jump() for Xo(ro)shiro as alternative to jump()
  providing fewer streams with longer period.
• Handle R's RNG scope properly during initialisation.
• New functions dqsample and dqsample.int using an unbiased sampling
  algorithm.
• Use R_unif_index() instead of unif_rand() to retrieve random data
  from R's RNG in generateSeedVectors().
• Scalar RNGs in the C++ API: dqrng::runif, dqrng::rnorm and dqrng::rexp