Fixing rna-transcription to match readme.

This fixes #3.

and fixes the lisp project specific problem mentioned in:
exercism/exercism#1310.

rna-transcription/example.lisp

@@ -9,6 +9,11 @@
 	     (coerce strand 'list))
       (signal 'error)))
 
+(defparameter dna->rna 
+  '((#\C . #\G) (#\G . #\C) (#\A . #\U) (#\T . #\A)))
+
 (defun to-rna (strand)
   (validate-strand strand)
-  (substitute #\U #\T strand))
+  (concatenate 'string
+	       (mapcar #'(lambda (c) (cdr (assoc c dna->rna))) 
+		       (coerce strand 'list))))

rna-transcription/rna-transcription-test.lisp

@@ -7,20 +7,20 @@
 
 (in-package :rna-transcription-test)
 
-(define-test transcribes-cytidine-unchanged
-  (assert-equal "C" (dna:to-rna "C")))
+(define-test transcribes-cytidine-to-guanosine
+  (assert-equal "G" (dna:to-rna "C")))
 
-(define-test transcribes-guanosine-unchanged
-  (assert-equal "G" (dna:to-rna "G")))
+(define-test transcribes-guanosine-to-cytidine
+  (assert-equal "C" (dna:to-rna "G")))
 
-(define-test transcribes-adenosine-unchanged
-  (assert-equal "A" (dna:to-rna "A")))
+(define-test transcribes-adenosine-to-uracile
+  (assert-equal "U" (dna:to-rna "A")))
 
-(define-test it-transcribes-thymidine-to-uracil
-  (assert-equal "U" (dna:to-rna "T")))
+(define-test it-transcribes-thymidine-to-adenosine
+  (assert-equal "A" (dna:to-rna "T")))
 
-(define-test it-transcribes-all-occurrences-of-thymidine-to-uracil
-  (assert-equal "ACGUGGUCUUAA" (dna:to-rna "ACGTGGTCTTAA")))
+(define-test it-transcribes-all-nucleotides
+  (assert-equal "UGCACCAGAAUU" (dna:to-rna "ACGTGGTCTTAA")))
 
 (define-test it-validates-dna-strands
   (assert-error 'error (dna:to-rna "XCGFGGTDTTAA")))