Adding collect function

- Collect function as fn:(collector, x) -> new_collector for collections
- Moving some definitions to "libs" folder
- Map and filter defined in mal

tests/arithmetic.mal

@@ -18,10 +18,6 @@
 (assert (= (/ -10 -2) 5))
 (assert (not (ok? (/ 12 0))))
 
-; mod
-(assert (= (mod 10 4) 2))
-(assert (= (mod 4 10) 4))
-
 ; >
 (assert (> 3 2))
 (assert (not (> 1 2)))
@@ -40,4 +36,4 @@
 ; <=
 (assert (<= 1 3))
 (assert (not (<= 3 2)))
-(assert (<= 1 1))
+(assert (<= 1 1))

tests/forms.mal

@@ -42,7 +42,7 @@
 (assert-fail '(if))
 
 ; let*
-(assert (let* [let-a 1
+(assert-eq (let* [let-a 1
                let-b 2]
     (assert-eq let-a 1)
     (assert-eq let-b 2)