clean up

doc/lazy_seq.md

@@ -0,0 +1,13 @@
+# Lazy Sequences
+When writing recursive functions like Fibonacci, it is often easier and faster to use
+lazy sequences.
+
+Example:
+```kt
+val fib = lazySequence(0 to 1) { i, f ->
+  f(i-1) + f(i-2)
+}
+
+println(fib[10])
+```
+Note: If we call f for any number below 0, it will call f(0) instead.