Restructure folders.

Author: trekhleb

README.md

@@ -30,14 +30,15 @@
 * **Math**
   * [Factorial](https://github.com/trekhleb/javascript-algorithms/tree/master/src/algorithms/math/factorial)
   * [Fibonacci Number](https://github.com/trekhleb/javascript-algorithms/tree/master/src/algorithms/math/fibonacci)
-  * [Cartesian Product](https://github.com/trekhleb/javascript-algorithms/tree/master/src/algorithms/math/cartesian-product) - product of multiple sets
-  * [Power Set](https://github.com/trekhleb/javascript-algorithms/tree/master/src/algorithms/math/power-set) - all subsets of the set
-  * [Permutations](https://github.com/trekhleb/javascript-algorithms/tree/master/src/algorithms/math/permutations) (with and without repetitions)
-  * [Combinations](https://github.com/trekhleb/javascript-algorithms/tree/master/src/algorithms/math/combinations) (with and without repetitions)  
   * [Primality Test](https://github.com/trekhleb/javascript-algorithms/tree/master/src/algorithms/math/primality-test) (trial division method)
   * [Euclidean Algorithm](https://github.com/trekhleb/javascript-algorithms/tree/master/src/algorithms/math/euclidean-algorithm) - calculate the Greatest Common Divisor (GCD)
   * [Least Common Multiple](https://github.com/trekhleb/javascript-algorithms/tree/master/src/algorithms/math/least-common-multiple) (LCM)
-  * [Fisher–Yates Shuffle](https://github.com/trekhleb/javascript-algorithms/tree/master/src/algorithms/math/fisher-yates) - random permutation of a finite sequence
+* **Sets**
+  * [Cartesian Product](https://github.com/trekhleb/javascript-algorithms/tree/master/src/algorithms/sets/cartesian-product) - product of multiple sets
+  * [Power Set](https://github.com/trekhleb/javascript-algorithms/tree/master/src/algorithms/sets/power-set) - all subsets of the set 
+  * [Permutations](https://github.com/trekhleb/javascript-algorithms/tree/master/src/algorithms/sets/permutations) (with and without repetitions)
+  * [Combinations](https://github.com/trekhleb/javascript-algorithms/tree/master/src/algorithms/sets/combinations) (with and without repetitions)
+  * [Fisher–Yates Shuffle](https://github.com/trekhleb/javascript-algorithms/tree/master/src/algorithms/math/fisher-yates) - random permutation of a finite sequence 
 * **String**
   * [Levenshtein Distance](https://github.com/trekhleb/javascript-algorithms/tree/master/src/algorithms/string/levenshtein-distance) - minimum edit distance between two sequences
   * [Hamming Distance](https://github.com/trekhleb/javascript-algorithms/tree/master/src/algorithms/string/hamming-distance) - number of positions at which the symbols are different

src/algorithms/math/cartesian-product/README.md src/algorithms/sets/cartesian-product/README.md

@@ -1,5 +1,5 @@
 import combineWithRepetitions from '../combineWithRepetitions';
-import factorial from '../../factorial/factorial';
+import factorial from '../../../math/factorial/factorial';
 
 describe('combineWithRepetitions', () => {
   it('should combine string with repetitions', () => {

src/algorithms/math/cartesian-product/__test__/cartesianProduct.test.js src/algorithms/sets/cartesian-product/__test__/cartesianProduct.test.js

@@ -1,5 +1,5 @@
 import combineWithoutRepetitions from '../combineWithoutRepetitions';
-import factorial from '../../factorial/factorial';
+import factorial from '../../../math/factorial/factorial';
 
 describe('combineWithoutRepetitions', () => {
   it('should combine string without repetitions', () => {

src/algorithms/math/cartesian-product/cartesianProduct.js src/algorithms/sets/cartesian-product/cartesianProduct.js

@@ -1,5 +1,5 @@
 import permutateWithoutRepetitions from '../permutateWithoutRepetitions';
-import factorial from '../../factorial/factorial';
+import factorial from '../../../math/factorial/factorial';
 
 describe('permutateWithoutRepetitions', () => {
   it('should permutate string', () => {