added canny edge detector for simplecv-js

![7](https://f.cloud.github.com/assets/3799830/446032/f53bac84-b1cb-11e2-84d9-b0e30be1ac03.jpg)
![30_60_3](https://f.cloud.github.com/assets/3799830/446044/31a6a836-b1cc-11e2-8fe8-f39e3aaad8d5.png)
![lens](https://f.cloud.github.com/assets/3799830/446051/484293b6-b1cc-11e2-9a44-592c47f1466d.jpg)
![lens](https://f.cloud.github.com/assets/3799830/446052/5120086a-b1cc-11e2-8f38-3ab53519a3d2.png)
![lo](https://f.cloud.github.com/assets/3799830/446053/5989a5d8-b1cc-11e2-9274-e840c2aaf460.jpg)
![lo](https://f.cloud.github.com/assets/3799830/446060/5feb98fa-b1cc-11e2-9741-8a86139318be.png)
![3](https://f.cloud.github.com/assets/3799830/446064/6e7d5110-b1cc-11e2-9ced-58c14d0861cc.jpg)
![30_60_3](https://f.cloud.github.com/assets/3799830/446066/75236d1a-b1cc-11e2-8a8a-f8ef56c174d4.png)
![8](https://f.cloud.github.com/assets/3799830/446073/905c0e34-b1cc-11e2-8ef0-70e171db1989.jpg)
![30_60_5](https://f.cloud.github.com/assets/3799830/446075/9ee27a10-b1cc-11e2-95ee-90f9d04ef399.png)