No grade bug fix

[diego-codes]

Closes #53

NOTE: This is a rebased PR from my original PR for IBM-Design/color-bee. I tried to be as thorough with my rebase to make sure it matches this project's structure. But there is chance, I might have missed something.

Problem

The assumption is that if I use the color function without a grade argument, I should get the core grade of the color I am requesting:

.foo {
  color: color('blue'); // Core grade is 50, so the color to return should be #2d74da
}

The default value for the $grade parameter in the color() function is set to 0 which currently no color has this as a possible grade. Updating the default $grade value to a number that does in fact exist in all palettes doesn't work because each color has a different core grade associated with it.

Solution

The solution I have come up with is to add one more grade item to each color map in the output _bee-palette.scss with the key of core and value of whatever that palette's core grade hex value is. This way we can set the default value for $grade in the color() function to 'core' and fulfill the expected behavior of calling the color() function without supplying a grade.

Along with this solutions, I took the liberty to:

• Update the .ase, .json, and .scl output templates to include the core grade value.
• Improve (fix?) error handling inside of the color() function to throw an error if the user provides a color or grade that does not exist as well as a warning if they're outside of the $alpha channel value range.
• Lastly, added unit tests for the color() function using True and Mocha! Sadly, I don't think there is a way to test for errors which would have been nice.

[seejamescode]

The original secure key is correct! I need to get a new one for color-bee.

[diego-codes]

Oops, my bad. Changed it back.

[seejamescode]

@ind1go or @Snugug, can you review the sass generation?

[seejamescode]

Also @cuyaproductions, does the Readme still reflect this or are there changes in calling the sass?

[diego-codes]

@seejamescode, I just updated the color examples on the README file to match the current color values and added a small section about running tests.

[panpan-lin]

Quite a lot of commits in this PR. Not sure about your team but in my team we are told to squash them into 1 or whatever number that actually makes sense, with the ticket number preceding by # as part of the commit message, so that the master branch's history is cleaner and easier to read.

[Snugug]

I'd like to help reviewing this PR, but It's way too large with way too many changes to sanely review. Please break this PR up. The issue at hand only mentions not being able to pass just a color name to a Sass mixin, yet I see a whole new testing framework, changes to docs, color palettes, Gulpfile, and sketch files. That's way more code than needed. I'd recommend the following:

• A single PR that just resolves Getting color throws an error if no grade is specified #53 only for Sass
• A single PR to add just Sass tests
• A single PR to update the docs
• A single PR for whatever the Sketch updates you're doing

[Snugug]

This PR is too large to review effectively and resolves much more than just the issue it's attached to. Please review my comments from #58 (comment) and resubmit