Update READMEs.

Author: trekhleb

src/algorithms/math/fibonacci/README.md

@@ -6,3 +6,15 @@ the fact that every number after the first two is the sum of the two
 preceding ones:
 
 `0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, ...`
+
+A tiling with squares whose side lengths are successive Fibonacci numbers
+
+![Fibonacci](https://upload.wikimedia.org/wikipedia/commons/d/db/34%2A21-FibonacciBlocks.png)
+
+The Fibonacci spiral: an approximation of the golden spiral created by drawing circular arcs connecting the opposite corners of squares in the Fibonacci tiling;[4] this one uses squares of sizes 1, 1, 2, 3, 5, 8, 13 and 21.
+
+![Fibonacci Spiral](https://upload.wikimedia.org/wikipedia/commons/2/2e/FibonacciSpiral.svg)
+
+## References
+
+[Wikipedia](https://en.wikipedia.org/wiki/Fibonacci_number)