Satisfy both conda-forge and defaults channel requirements

[183amir]

This pull allows me to install opencv alongside anaconda=4 while also allowing other versions for conda-forge channel consistency.

[conda-forge-linter]

Hi! This is the friendly automated conda-forge-linting service.

I wanted to let you know that I linted all conda-recipes in your PR (recipe) and found some lint.

Here's what I've got...

For recipe:

• Failed to even lint the recipe (might be a conda-smithy bug) 😢

[jakirkham]

Let's hold on this for a bit. I'm trying to see if we can get a bit more inline with defaults by downgrading some of these packages. We already have some problems like qt dependency compatibility issues, which we somehow need to address.

[183amir]

This is not going to break anything, it will just add more flexibility.

[183amir]

The Linux build is broken because of loose dependency tracking of jpeg in jasper:

jasper 1.900.1 0 linux-64          : jpeg
jasper 1.900.1 1 linux-64          : jpeg
jasper 1.900.1 2 linux-64          : jpeg 9b

[jakirkham]

It will eat up a bunch of build time though. If you try to add this to OpenCV 3.x, it won't work as we are already near the limit with CircleCI. Again let's please hold on this and figure out what we can do with these image libraries so we are not so out of sync with defaults.