Clean up API

docs/contribution-guidelines.md

@@ -12,6 +12,51 @@
 
 *   Follow the `TSLint` rules
 
+## Add vs Create
+
+This is just a guideline, and the rules can sometimes be broken.
+
+*   Use `create` if the method `new`'s up an element inside:
+
+    ```js
+    public createParagraph() {
+        const paragraph = new Paragraph();
+        this.root.push(paragraph);
+    }
+    ```
+
+*   Use `add` if you add the element into the method as a parameter:
+
+    ```js
+    public createParagraph(paragraph: Paragraph) {
+        this.root.push(paragraph);
+    }
+    ```
+
+## Getters and Setters
+
+Getters and Setters are done with a capital letter like so:
+
+```js
+public get Level() {
+
+}
+```
+
+There is no performance advantage by doing this. It means we don't need to prefix all private variables with the ugly `_`:
+
+**Do not:** 
+
+```js
+private get _level: string;
+```
+
+**Do** 
+
+```js
+private get level: string;
+```
+
 ## Testing
 
 Please write a test of every file you make and suffix it with `.spec.ts`.