Golangci linting cleanup

[kensipe]

A number of cleanups. Resisted several which were too opinionated and thought might be contentious. This resulted in a bug fix around len(review)
Fixes:

• remove unnecessary casts
• switch to non f formatting func for non formatting strings
• added error handling for non-contentious instances

Things to think about:

1. There are casts out of mysql and postgress wich are not checked
2. The template.JS(s) is not escaped and likely should change to JSEscapeString or place a // no lint comment that it has been evaluated to be ok
3. The time.Time return from cachedIssueComments and cachedReviews is never used
4. cyclomatic complexity is high for hubbub/item.go:33 and hubbub/match.go:15. These should be refactor IHMO

Signed-off-by: Ken Sipe kensipe@gmail.com

[tstromberg]

Thank you!