Docstring for Series missing description on 'fastpath'
The Series docstring does not include any description for the 'fastpath' parameter. 

Couldn't find any example on the website that used this parameter, not sure which needs updating: the init definition or the parameters section.

![image](https://cloud.githubusercontent.com/assets/3363363/2733732/0e121c32-c64a-11e3-8b89-74f0e0457d5e.png)
![image](https://cloud.githubusercontent.com/assets/3363363/2733695/a428f8ae-c649-11e3-9b02-bdc7853238f9.png)
