fix: Update CI so that Appveyor builds correctly
fix: Update CI so that Appveyor builds correctly

* install requirements with pip

* don't update conda a second time

* create a new environment for testing

* use % for variable expansion for powershell

* don't create a new test environment

cmshobe/landlab,cmshobe/landlab,landlab/landlab,landlab/landlab,landlab/landlab,cmshobe/landlab,amandersillinois/landlab,amandersillinois/landlab