[matplotlib-devel] Patch for errorbar, alpha kw did not apply to lines and cap markers

Hi matplotlib developers,

this is my first commit to matplotlib. I am using it heavily in a 
scientific context. I followed the How-to and send you an according 
patch for what I consider a bug. If it doesn't make sense, please be 
lenient with me for now, since it my first time. : )

As described in the subject line, I made the alpha keyword in the 
errorbar command act also on the error bars and not only on the markers. 
The previous behaviour seemed inconsistent.

Cheers,
Hans