Fix typo code of isNumber

// BEFORE
var isNumber = require('101/is-number');

['foo', 'bar', 1].map(isString); // [false, false, true]

// AFTER
var isNumber = require('101/is-number');

['foo', 'bar', 1].map(isNumber); // [false, false, true]
Merge pull request #41 from Hx0A5F/patch-1

Fix typo code of isNumber