Add Configuration#use_exception_level_filters option

[jondeandres]

Let the users to set a global use_exception_level_filters option

Usage:

Rollbar.configure do |config|
  config.use_exception_level_filters = true
end

By default the setting is false so we keep the current interface

Fix #587

[rokob]

This seems fine to me. I guess the only question is whether you want this global configuration setting to be overridable on a per-call basis, i.e. if use_exception_level_filters is true in the configuration, based on this code, you cannot add :use_exception_level_filters => false on a particular error call and expect that to work. I think that is okay and conforms to what I would expect by setting the global flag. So I'd say go ahead and merge this, once you fix the tests.

[brianr]

Hm I think I would expect that:

• the new flag @jondeandres added is the default
• the default can be overridden by passing a param in the call

What if we do something like:

• rename the new config param to use_exception_level_filters_default. Its default will be false to maintain the current behavior.
• if you don't pass the :use_exception_level_filters param in a call, then the value of the config param is used. (maybe do this by having the param default to nil)
• if you do pass the :use_exception_level_filters param, then the value you provide is used

[jondeandres]

@brianr @rokob I've pushed force here with Brian's suggestions.

[rokob]

This is missing a test when config.use_exception_level_filters_default = true has been set, and when :use_exception_level_filters => false is passed in with the Rollbar.error call.

[rokob]

I added one

[rokob]

I squashed those commits.