Bump irb version to 1.1.0.pre.1.

Becausee the current irb support reline and have many of changes.

lib/irb/version.rb

@@ -11,7 +11,7 @@
 #
 
 module IRB # :nodoc:
-  VERSION = "1.0.0"
+  VERSION = "1.1.0.pre.1"
   @RELEASE_VERSION = VERSION
-  @LAST_UPDATE_DATE = "2018-12-18"
+  @LAST_UPDATE_DATE = "2019-05-31"
 end