Allow gem versions to contain a string

ignisf · ignisf · commit 275d883b8cf4 · 2016-05-12T18:09:16.000+03:00
This was causing issues when determining the upstream v8 version from an
rc version of the gem
diff --git a/ext/libv8/builder.rb b/ext/libv8/builder.rb
@@ -90,7 +90,7 @@ def setup_python!
     # then this will be 4.5.95
     #
     def source_version
-      Libv8::VERSION.gsub(/\.\d+$/, '')
+      Libv8::VERSION.gsub(/\.[^.]+$/, '')
     end
 
     ##
