Update include/SFGUI/Config.hpp Version Information

[drako0812]

I noticed that the current release is 0.4.0 but the file still defines the version as 0.3.1

EDIT: Noticed that this was mentioned in #73 but it apparently still hasn't been merged.

[DrBarbare]

Oh yeah, I need to open a new PR for that. I had not thought about checking the headers though :p. I'll try to open something now.