Refactor: The Projector Can Now Start Itself

Why This Change Is Necessary
========================================================================

Progress events are now being called properly on the projector and
therefore `Progress` no longer needs to do it.

What These Changes Do To Address the Issue
========================================================================

Stop calling projector start when progress starts.

Side Effects Caused By This Change
========================================================================

None expected.

lib/ruby-progressbar/progress.rb

@@ -19,7 +19,6 @@ def initialize(options = {})
   end
 
   def start(options = {})
-    running_average_calculator.start
     self.progress = \
       self.starting_position = options[:at] || progress
   end

spec/lib/ruby-progressbar/progress_spec.rb

@@ -124,6 +124,7 @@ class    ProgressBar
     progress   = Progress.new(:total => 50, :projector => projector)
 
     projector.__send__(:projection=, 10)
+    projector.start
     progress.start :at => 0
 
     expect(progress.running_average).to be_zero
@@ -138,6 +139,7 @@ class    ProgressBar
     progress   = Progress.new(:total => 50, :projector => projector)
 
     projector.__send__(:projection=, 10)
+    projector.start
     progress.start :at => 0
 
     expect(progress.running_average).to be_zero