send errors in homepage updater to sentry

[chadwhitacre]

Exceptions during homepage updating don't end up in Sentry, and it'd be nice if they did.

Reticketed from #1598.

[chadwhitacre]

I'm not adding this to Infrastructure because it's not a big systemic issue. We want the homepage updater to go away through one of various ways:

• we upgrade to 9.3 (upgrade to Postgres 9.3 #1158) and replace the updater with a materialized view
• we redo our db schema (Clean up db schema #1549) and have fast reads w/o a view
• we redesign the homepage (revamp homepage (inc. community pages) #1074) and don't show new participants in the same way anymore

[chadwhitacre]

Done!