Add note about channel_priority=strict to docs

[tlambert03]

Thanks again for your efforts on #25 and #27 ... I was able to build the environment on both mac and linux. however, it didn't work at first, and it was only after a while that I figured out the problem was the channel_priority=strict setting in my conda config. Since that is both the recommended setting from conda (will be default in 5.0), and since it is encouraged in the conda-forge install, I suspect that many of your users will probably have that config set. I tried for a while to get a working environment.yml even with that setting (by prepending each dependency with a specific channel), but I never succeeded. So, you may want to add a note to your install instructions that users should temporarily disabled channel_priorty=strict

[jburel]

Thanks for the heads up
I have it off by default. I will add a note.
I hope not to have to juggle between the various ilastik conda channels when we upgrade to the latest. Notebooks/scripts are still not working due to a problem with ilastik itself.