add a new post on riemann
Restyle line numbers

CSS changes to line numbers in code blocks

 * Move line numbers away from the code

 * Make line numbers gray

 * Add vertical whitespace after code blocks

Signed-off-by: Don Marti <dmarti@cloudius-systems.com>
Minor edits

 * Usage/consistency/spelling

 * Add calls to action at the end (mailing list, GitHub)

 * Author Twitter link

Signed-off-by: Don Marti <dmarti@cloudius-systems.com>
Merge branch 'riemann-on-osv-post' into source
Meetup photo and blog item

Signed-off-by: Don Marti <dmarti@cloudius-systems.com>