Added cond function to Userlib

Added the cond function to Userlib, also added the associated tests
and documentation.

Writing.org

@@ -126,6 +126,29 @@ Example:
      (eq? (some-big-calculation) expected-result))
 #+END_SRC
 
+*** Cond
+*Cond* is a function defined in the *Userlib* that acts as syntax sugar for nested *if form*s.
+Given a list of pairs consisting of a condition and a form to execute *cond* will iterate trough the list evaluating the conditions in order, Upon encountering a condition that evaluates to ~true~ the corresponding form will be evaluated and its result returned, thus halting the loop so no further forms are evaluated.
+If no conditions evaluate to true then *cond* won't execute anything
+The argument to *cond* must be given using *quote*, otherwise it will be evaluated before being passed to *cond*, thus making it not work.
+
+Example:
+#+BEGIN_SRC lisp
+  (let ((list (1 2 3 4)))
+    (cond (q
+	   (((gt? (car list) 2) (echo "The first number of this list is greater than 2")) ;; The first condition returns false so this expression won't be evaluated
+	    ((gt? (len list) 3) (echo "This list's length is greater than 3" )) ;; Since the second condition returns true this form will be evaluated and its result will be returned
+	    (true (echo "This list is rather unremarkable")))))) ;; This form will be evaluated if none of the previous conditions return true
+
+  ;; This is what the equivalent if form would look like
+  (let ((list (1 2 3 4)))
+    (if (gt? (car list) 2)
+	(echo "The first number of this list is greater than 2")
+	(if (gt? (len list) 3)
+	    (echo "This list's length is greater than 3")
+	    (echo "This list is rather unremarkable"))))
+#+END_SRC
+
 *** Not quite control flow
 Several other functions use lazy evaluation of their arguments. The below list is non-exhaustive:
 - toggle
@@ -274,7 +297,7 @@ The following table is up to date as of Relish 0.3.0. For latest information try
 |----------------+---------------+----------------+---------+--------+-----------+-----------+-----------+--------|
 |                | set?          | fg             | dq      | div    | concat    | or        | get-paths |        |
 |----------------+---------------+----------------+---------+--------+-----------+-----------+-----------+--------|
-|                |               |                | pop     | gte?   | string    |           |           |        |
+|                |               |                | pop     | gte?   | string    |           | cond      |        |
 |----------------+---------------+----------------+---------+--------+-----------+-----------+-----------+--------|
 |                |               |                |         | int    |           |           |           |        |
 |----------------+---------------+----------------+---------+--------+-----------+-----------+-----------+--------|