Feature request #1653: Given input "foo.html.tmpl", compile to "foo.html.rb" and fill to "foo.html"

As things work right now:

• Input foo.tmpl
• Compiles to foo.rb
• And fills to foo.html

Walrus provides an -e switch to override the output extension when filling, but it would be convenient to instead be able to do something like:

$ walrus fill *.tmpl

And have it automatically turn a directory like this:

display.css.tmpl
index.html.tmpl
about.html.tmpl

Into:

display.css.rb
index.html.rb
about.html.rb

And then:

display.css
index.html
about.html