converted plugin load failtures from exceptions to warnings, bump to version 0.9.3pre1

lib/pry/plugins.rb

@@ -27,7 +27,7 @@ class Pry
         begin
           require gem_name
         rescue LoadError
-          raise PluginNotFound, "The plugin '#{gem_name}' was not found!"
+          $stderr.puts "Warning: The plugin '#{gem_name}' was not found!"
         end
         self.active = true
         self.enabled = true

lib/pry/version.rb

@@ -1,3 +1,3 @@
 class Pry
-  VERSION = "0.9.2"
+  VERSION = "0.9.3pre1"
 end