Don't wrap blame <li> in a <pre>, so we can reenable prettify

We were already setting the font to match the <pre> section on the
RHS, so this is unnecessary. This alleviates most of the performance
hit associated with running prettify in blame, so turn that back on.

Include line numbers even when we haven't auto-detected the language,
addressing Issue 45.

Change-Id: I9f1b96b593bc510e882ddf4fd5de406f5409a2be
3 files changed