italics play nicely with asterisk but not underscore

[nedtwigg]

• *italic* works
• _italic_ gets out of sync
• bold

Possible solutions:

• fix it
• auto-replace _ with *, maybe give a little notice the first time pointing to this issue?

[nedtwigg]

for monospace fonts

• sometimes bold & italic can work, sometimes not (e.g.)

for variable-width fonts

• very hard to see how to bold could ever work reliably
• italic could maybe work, but it's inconsistent if bold doesn't
• so we're going to use only color to make this distinction Change colors to match GitHub's theming #11