Avoid freakoutery on invalid delims.

The specs tests assumes an implementation will silently ignore invalid delims.
I think that's a bad idea, so I throw an exception on invalid delims. So I just
ignore those "tests".

src/test/java/com/samskivert/mustache/specs/SpecRunner.java

@@ -4,12 +4,8 @@
 
 package com.samskivert.mustache.specs;
 
-import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
-import java.lang.reflect.Modifier;
 import java.util.ArrayList;
-import java.util.Collection;
-import java.util.HashSet;
 import java.util.List;
 import java.util.Map;