apply 'format' to args before passing to .Exception

eval this in repl.  the luminosity value is out of range.
(create-color {:h 1.0 :s 1.0 :l 111.0})

Before this change, the exception was thrown:
IllegalArgumentException No matching ctor found for class java.lang.Exception  clojure.lang.Reflector.invokeConstructor (Reflector.java:183)

"Exception has no constructor which takes a clojure.lang.ArraySeq, and it is an ArraySeq which is being passed to the Exception constructor."

After the change, the exception thrown is:
"Exception Elements must be of the form:
H (Hue): Float value in the range of: 0.0 - 360.0
S (Saturation): Float value in the range: 0.0 - 100.0
L (Lightness or Luminance): Float value in the range 0.0 - 100.0
1.0 1.0 111.0  sun.reflect.NativeConstructorAccessorImpl.newInstance0 (NativeConstructorAccessorImpl.java:-2)"

Much better...
Merge pull request #2 from austinjones/master

"throw-if-not" accidentally throws IllegalArgumentExceptions