MAINT: Drop pycalphad conda channel

[bocklund]

Checklist

• If any dependencies have changed, the changes are reflected in the
  • setup.py
  • environment-dev.yml

cyipopt is now building on conda-forge for Windows (thanks @moorepants!) so users installing pycalphad via Anaconda do not require the pycalphad channel anymore.

This PR

• bumps pycalphad's dependency on cyipopt to v0.3 or later (the version required for Windows support)
• removes the pycalphad channel from the installation instructions.

Since this PR updates the installation instructions, we should not merge it until conda-forge/pycalphad-feedstock#33 is merged and the package has propagated to the conda-forge channel.

[codecov]

Codecov Report

Merging #297 (ed165ce) into develop (d217b4b) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop     #297   +/-   ##
========================================
  Coverage    86.77%   86.77%           
========================================
  Files           46       46           
  Lines         4461     4461           
========================================
  Hits          3871     3871           
  Misses         590      590           

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[bocklund]

The conda-forge pycalphad package has been built and is now available (conda-forge/pycalphad-feedstock#33). I tested that it installs and works locally. This is ready for review.