standardize on "Rscons" capitalization

lib/rscons/builders/program.rb

@@ -1,6 +1,6 @@
 module Rscons
   module Builders
-    # A default RScons builder that knows how to link object files into an
+    # A default Rscons builder that knows how to link object files into an
     # executable program.
     class Rscons::Builders::Program < Rscons::Builder
       def default_variables(env)