added headers in usage section

README.md

@@ -12,6 +12,7 @@ Javascript eXtended Random number generator
     var JXRand = require('JXRand');
 ```
 
+### getNumber
 To get a random integer between 10 and 20:
 
 ```js
@@ -21,6 +22,7 @@ To get a random integer between 10 and 20:
 The `type` property is optional with a default value of `float`.
 For now the supported types are `integer` and `float`.
 
+### getInterval
 To get a random interval, with integer endpoints between 0 and 100 and length between 10 and 50:
 
 ```js
@@ -37,6 +39,7 @@ A possible value of `randomInterval` is `[43, 75]`.
 
 The `minLength`, `maxLength` and `type` properties are optional.
 
+### getElement
 To get a random element from a given array:
 
 ```js
@@ -45,6 +48,7 @@ To get a random element from a given array:
 
 The `randomElement` should now contain one random element of the array.
 
+### getRandomValuesObject
 In case we want to create an object with random values in custom keys, we can use `getRandomValuesObject`.
 
 We are using an array of objects as an argument where each object should contain the `name` of the key and the `type` of the random value.