cheapr 0.9.1

• New function recycle to help recycle R objects to a common size.

• The set functions that update by reference are now ALTREP aware and
  take a copy when the input is an ALTREP object.

• New function lag2_ as a generalised solution for complex lags. It supports
  dynamic lag vectors, lags using an order vector, and custom run lengths.
  It doesn't support updating by reference or long vectors.