Support conditional readers

[mcuervoe]

Scittle does not currently support conditional readers; that is, you can not load .cljc files with #?(:cljs ...) expressions. The conditional readers seem to have been filtered out when you execute the code in the browser.

To test it, replace any ccojureScript expression with #?(:cljs expression), for example

replace ;(js/alert "You clicked!") with #?(:cljs (js/alert "You clicked!"))

The net result should be the same if conditional readers work as expected.

@borkdude , thanks as always for such great tools you build