Fix params filtering

Neither Symbol nor String in Ruby has `#in?` method.
So this filtering raises another exception instead
of sending it:

    Exception while reporting exception to Rollbar:
    undefined method `in?' for :session_id:Symbol

This patch fixes expressions to by Rubista not Pythonista :D
bump version to 0.9.7, update changelog, add @ixti to THANKS, convert thanks file to markdown.