- Memoize whether or not stderr and stdout logging is being captured in the Outputter.
- Profiler suggests a small performance boost
Make use of static methods instead Formatter instead of instance methods inside the Formatter singleton.  This should boost performance a little bit.
Fix typo in formatter.rb to use class variable @@caller_enabled
- Bump version number to 2.1.0
- Avoiding using smart_backtrace_log_level() in the logger should produce a very, very small performance boost.