fix top text annotation collision with note head

Added test for text annotation with stems up and down. fixed the problem with top text annotation. still there are problems with the bottom annotation that I couldn't solve.

images are the tests of the 
![after](https://f.cloud.github.com/assets/4021701/2238881/8d26d3c8-9c06-11e3-95d7-35776ba16088.jpg)
![before](https://f.cloud.github.com/assets/4021701/2238882/8d28da9c-9c06-11e3-9550-ac7791b62121.jpg)

 annotation before and after the commit