Drawing pu

Was pu #192

## Overview

 - Created PointInfo struct reference in API type casting.
 - Assigned / mapped arguments for wand library methods.
   - [DrawPolygon](http://www.imagemagick.org/api/drawing-wand.php#DrawPolygon)
   - [DrawPolyline](http://www.imagemagick.org/api/drawing-wand.php#DrawPolyline)
   - [DrawBezier](http://www.imagemagick.org/api/drawing-wand.php#DrawBezier)
 - Completed initial unit test & documentation.

### Examples

**Drawing.polygon**

```python
with Image(filename="crosshatch.png") as img:
    with Drawing() as draw:
        draw.fill_color = Color("#fff")
        draw.stroke_color = Color("#000")
        draw.stroke_width = 2
        points = [(5,5),(45,40),(45,10),(5,45)]
        draw.polygon(points)
        draw.draw(img)
        img.save(filename="polygon.png")
```
![Drawing.polygon](http://emcconville.com/Polyline/polygon.png)

**Drawing.polyline**

```python
with Image(filename="crosshatch.png") as img:
    with Drawing() as draw:
        draw.fill_color = Color("transparent")
        draw.stroke_color = Color("#000")
        draw.stroke_width = 2
        points = [(5,5),(45,40),(45,10),(5,45)]
        draw.polyline(points)
        draw.draw(img)
        img.save(filename="polyline.png")
```
![Drawing.polyline](http://emcconville.com/Polyline/polyline.png)

**Drawing.bezier**

```python
with Image(filename="crosshatch.png") as img:
    with Drawing() as draw:
        draw.fill_color = Color("transparent")
        draw.stroke_color = Color("#000")
        draw.stroke_width = 2
        points = [(5,5), (0,50), (50,0), (45,45)]
        draw.bezier(points)
        draw.draw(img)
        img.save(filename="bezier.png")
```
![Drawing.bezier](http://emcconville.com/Polyline/bezier.png)