Updating styles for docs site

This MR addresses the following:

• Fixes issues with spacing (above and below items) in bulleted and ordered lists.
• Updates heading styles (font size, padding, and removes the line from underneath them).
• Moves tier badges to the left so they aren't floating (now that the underlines are gone beneath headings).
• Removes extra padding around images, as well as the shadow. Instead, uses a thin grey line around images.
• Updates alert boxes (notes, tips) and block quotes to have a thin slightly-rounded outline, and updates colors.
• Makes breadcrumbs smaller.
• Makes body text 1px smaller.

Bullet spacing screenshots

Before	After
Each line of bullet text had the same amount of space below it:	Now each bullet is more obviously together:
Between text and bullets, there was extra space:	Now the space is similar to what it is between paragraphs.

Heading styles & tier badges

We went with these styles to try to better differentiate heading levels. (We wanted bigger gaps between each heading level.)

Heading	In this MR	On site before
Body	14px	15px
H1	34px	30px
H2	28px	28px
H3	23px	24px
H4	18px	22px
H5	16px black	20px grey
H6	14px black	18px grey

H1 with tier

Before	After

Image padding/outlines

Before	After
Image has a shadow and lots of padding above and below:	Now has grey outline (same as table color) and just a bit less padding:

Breadcrumbs

Before	After
16px	15px

Alert boxes

New colors:

Before	After
Note
Tip
Caution
Danger

Closes #701 (closed)