Output to window is rendering using different colors than output to file

[mattpenner]

I am running version 0.5.0 on Windows 10.

When I navigate to a folder with my STLs and enter the following command I get the following output in a window:
"c:\Program Files\stl-thumb\stl-thumb.exe" -b FFFFFFFF -m 000000 111111 FFFFFF -x Core_Clamp_C_Primo.STL Core_Clamp_C_Primo.PNG

However, when I run the exact same command, but without the -x parameter, I get the following output in the PNG file:

[unlimitedbacon]

I think this is because we are not converting between rgb and srgb properly.