Optimize our requires

Avoid requiring things that are already defined. Rubygems is very slow at traversing the filesystem.

Signed-off-by: Tim Smith <[email protected]>

Rakefile

@@ -24,7 +24,7 @@ rescue LoadError
 end
 
 begin
-  require "yard"
+  require "yard" unless defined?(YARD)
   YARD::Rake::YardocTask.new(:docs)
 rescue LoadError
   puts "yard is not available. bundle install first to make sure all dependencies are installed."
@@ -33,7 +33,7 @@ end
 task :console do
   require "irb"
   require "irb/completion"
-  require "mixlib/cli"
+  require "mixlib/cli" unless defined?(Mixlib::CLI)
   ARGV.clear
   IRB.start
 end

lib/mixlib/cli.rb

@@ -16,7 +16,7 @@
 # limitations under the License.
 #
 
-require "optparse"
+require "optparse" unless defined?(OptionParser)
 require_relative "cli/formatter"
 module Mixlib