DOC: Small README tidying

[fedarko]

Reading through this again, and noticed a few things we could make a bit clearer.

• Replace ’ character with ' character (this accounts for most of the line changes in this PR)

• Split up the paragraph describing searching for a node to "break" around the figure, which IMO reads a bit clearer:

Before	After

• In the barplots section:
  • "this is the same information as we showed when coloring the tree by feature metadata earlier" -> "this is the same information we saw when coloring the tree's nodes by Level 2 earlier"
  • "We know from the barplot that this tip is only present in one right palm sample, and the Sample Presence Information summary by body-site for this tip confirms this." --> "We know from the barplot that this tip is only present in right palm sample(s), and the Sample Presence Information summary by body-site for this tip confirms this: this particular tip is only present in one right palm sample."

[emperor-helper]

The following artifacts were built for this PR: empire-biplot.qzv, empire.qzv, empress-tree.qzv, just-fm.qzv, plain.qzv

[ElDeveloper]

Thanks @fedarko