Add tasks for all the new languages

Task/Substring/Wart/substring.wart

@@ -0,0 +1,22 @@
+s <- "abcdefgh"
+s.0
+=> "a"
+
+# starting from n characters in and of m length;
+def (substr s start len)
+  (s start start+len)
+(substr s 3 2)
+=> "de"
+
+# starting from n characters in, up to the end of the string
+(s 3 nil)
+=> "defgh"
+
+# whole string minus last character;
+(s 3 -1)
+=> "defg"
+
+# starting from a known character within the string and of <tt>m</tt> length;
+# starting from a known substring within the string and of <tt>m</tt> length.
+let start (pos s pat)
+  (s start start+m)