Updated copyright date for 2018
Updated copyright date for 2018

Flix01/imgui,ocornut/imgui,cmaughan/imgui,ggtucker/imgui,mikesart/imgui,nProtect/imgui,ocornut/imgui,bkaradzic/imgui,ocornut/imgui,Flix01/imgui,burningreggae/imgui,burningreggae/imgui,ggtucker/imgui,nProtect/imgui,dougbinks/imgui,wflohry/imgui-addons,cmaughan/imgui,Flix01/imgui,bkaradzic/imgui,bkaradzic/imgui,mikesart/imgui,cmaughan/imgui,dougbinks/imgui,nProtect/imgui,cmaughan/imgui,wflohry/imgui-addons,aimotive/imgui-glfw,ggtucker/imgui,aimotive/imgui-glfw