Modernize theme

[vanillajonathan]

Visual refresh of the theme to modernize it.

[vanillajonathan]

@Ionaru Change the border color from #bbb and #ddd to #ced4da so that it matched Bootstrap.

[Ionaru]

"Modern" is subjective, I don't think we should touch look of the editor until #447.

[vanillajonathan]

Yes, it is subjective. This modification does away with the borders and use a more flat style. Try it and see if you like it.

Might be something for the new editor.

For the current version might want to consider just changing the border color though, because now it doesn't match with the border color of the form-control class in Bootstrap, also it uses two different colors for borders, it uses both #bbb and #ddd resulting in the border of the toolbar being darker than other border of the editor which seems rather odd and might not be the intended look.

[Ionaru]

The editor was never made to integrate perfectly with Bootstrap. The design is purposefully minimal and can be easily edited by website creators to match their website theme. I don't think it's a good idea to copy over all the colours that bootstrap (currently) uses.

[vanillajonathan]

Then consider at least being consistent in the border color that is used, because now EasyMDE uses two different border colors, both #bbb and #ddd so it looks inconsistent and off. It looks like a "design bug" that was never intended.

[Ionaru]

I agree it's good to be consistent. I'll leave the choice between #bbb and #ddd up to you.

[vanillajonathan]

I would prefer #ced4da as that is what is used in Bootstrap. Else #ccc would be between #bbb and #ddd and closer to Bootstrap's #ced4da color.

But this PR was to modernize the theme and also includes other changes such as flat border-less buttons with more rounded corners. So this PR can be for EasyMDE v3.

I opened a new PR that only fixes the inconsistent border color at #466.