Only recast if datetime; use astype instead of view
Merge pull request #5998 from TomAugspurger/interpolate-datetime-fix

BUG: use astype for scipy datetime interpolation
TST: add regression test for interpolate #5977
BLD: make scatter_ci after_script.sh standalone
TST: add skip_scipy
TST: add skip_pchip
ENH: Add array_equivalent, to address the handling of NaNs when comparing arrays for equality.
Added equals method for Series and DataFrames