fix @no-clobber breaking process management

@no-clobber does not call Setup#call *at all*, which causes the
process monitor to not be listening to process events

lib/aruba/api/core.rb

@@ -25,8 +25,8 @@ def aruba
       # This will only clean up aruba's working directory to remove all
       # artifacts of your tests. This does NOT clean up the current working
       # directory.
-      def setup_aruba
-        Aruba::Setup.new(aruba).call
+      def setup_aruba(clobber: true)
+        Aruba::Setup.new(aruba).call(clobber: clobber)
 
         self
       end

lib/aruba/cucumber/hooks.rb

@@ -20,6 +20,10 @@
   aruba.command_monitor.clear
 end
 
+Before('@no-clobber') do
+  setup_aruba(clobber: false)
+end
+
 Before('~@no-clobber') do
   setup_aruba
 end

lib/aruba/setup.rb

@@ -10,10 +10,10 @@ def initialize(runtime)
       @runtime = runtime
     end
 
-    def call
+    def call(clobber: true)
       return if runtime.setup_already_done?
 
-      working_directory
+      working_directory(clobber: clobber)
       events
 
       runtime.setup_done
@@ -23,8 +23,10 @@ def call
 
     private
 
-    def working_directory
-      Aruba.platform.rm File.join(runtime.config.root_directory, runtime.config.working_directory), :force => true
+    def working_directory(clobber: true)
+      if clobber
+        Aruba.platform.rm File.join(runtime.config.root_directory, runtime.config.working_directory), :force => true
+      end
       Aruba.platform.mkdir File.join(runtime.config.root_directory, runtime.config.working_directory)
       Aruba.platform.chdir runtime.config.root_directory
     end