244: Remove Singularity

[evanmwillhite]

Addresses #244

Along with fourkitchens/emulsify-gulp#78, this PR removes singularity for layout and replaces it with a flexbox implementation with a CSS Grid one commented out.

What it does

1. Removes singularity references and implementation in main layout file
2. Implements a simple flexbox layout instead
3. Adds a CSS Grid layout that is commented out

To Test

1. Checkout this branch and link the Emulsify Gulp instance with the corresponding branch
2. View the sidebar template and full-width template and ensure content is displayed correctly at all screen sizes

[ModulesUnraveled]

@evanmwillhite This looks great! Thanks for including the css grid variation. I learned a lot just from playing with it.

As long as your okay with my changes, this is ready to merge!

[evanmwillhite]

I added this back, because it is needed for the non-sidebar layout

[evanmwillhite]

I like what's been done here, but I personally prefer to use space for bottom margins between things. I also like it to be space-double instead of just space visually. If you prefer to have these be the same, let's make a gutter-double that uses space-double. We could also just use space for all of these instead of making our own vars just for this file. What do you think?

[ModulesUnraveled]

I'm fine with this the way it is. This is just an example after-all. :)

[ModulesUnraveled]

I think the more vs less vertical space is probably a personal preference thing, so I'm not going to push back.

Let's !

[evanmwillhite]

I made some tweaks and added some comments. Let me know what you think.