* master: (31 commits)
  Add quantile method to GroupBy (pydata#2828)
  rolling_exp (nee ewm) (pydata#2650)
  Ensure explicitly indexed arrays are preserved (pydata#3027)
  add back dask-dev tests (pydata#3025)
  ENH: keepdims=True for xarray reductions (pydata#3033)
  Revert cmap fix (pydata#3038)
  Add "errors" keyword argument to drop() and drop_dims() (pydata#2994) (pydata#3028)
  More consistency checks (pydata#2859)
  Check types in travis (pydata#3024)
  Update issue templates (pydata#3019)
  Add pytest markers to avoid warnings (pydata#3023)
  Feature/merge errormsg (pydata#2971)
  More support for missing_value. (pydata#2973)
  Use flake8 rather than pycodestyle (pydata#3010)
  Pandas labels deprecation (pydata#3016)
  Pytest capture uses match, not message (pydata#3011)
  dask-dev tests to allowed failures in travis (pydata#3014)
  Fix 'to_masked_array' computing dask arrays twice (pydata#3006)
  str accessor (pydata#2991)
  fix safe_cast_to_index (pydata#3001)
  ...