Add support for runtime ratio object

[jianlingzhong]

everything should work.

❯ build/jank repl
Bottom of clojure.core
clojure.core=> (+ 1/2 1/3)
5/6
clojure.core=> (- 1/2 1/3)
1/6
clojure.core=> (* 1/2 1/3)
1/6
clojure.core=> (/ 1/2 1/3)
3/2
clojure.core=> (+ 1/2 1/2)
1
clojure.core=> (+ 1/2 1)
3/2
clojure.core=> (+ 1 1/3)
4/3
clojure.core=> (+ 1.0 1/3)
1.3333333333333333
clojure.core=> (+ 1.0 -1/3)
0.6666666666666667
clojure.core=> (* 1.0 -1/3)
-0.3333333333333333
clojure.core=> (> 1 1/3)
true
clojure.core=> (< 1 1/3)
false
clojure.core=> (== 1 1/1)
true
clojure.core=> (== 2 1/2)
false
clojure.core=> (mod 4/5 2)
0.8
clojure.core=> (mod 0.8 2)
0.8
clojure.core=> (mod 16/5 2)
1.2000000000000002
clojure.core=> (mod 16/5 3/2)
0.20000000000000018
clojure.core=> (mod (/ 16.0 5) (/ 3.0 2))
0.20000000000000018
clojure.core=> (<= (/ 1.0 3) 1/3)
true
clojure.core=> (== 1/3 0.3333)
false
clojure.core=> (== 1/3 0.3333333333333333333333)
true

this closes #66.