So I managed to get gtkmm working on Visual Studio 2015, the instructions are super unclear so here's what I did:
1- Download the x64 or x86 release from (do not follow the compilation instructions) https://github.com/codekiddy2/Visual-Studio-gtkmm
Releases: https://github.com/codekiddy2/Visual-Studio-gtkmm/releases
2- Save and extract everything... somewhere, like in the root of C:\
3- edit the props file in the extracted folder and change the path to where you put the files.
4- Open VS, open the straights project, go to View > Other Windows > Property Manager and add the props file you just edited in step 3.
5- If you downloaded the x64 library, you need to change the compilation target from x86 to x64 (In project properties > platform, and add the x64 platform) http://puu.sh/pV37k/c5bd3d651c.png
6- You may need to add the gtkmm folder you just downloaded to your PATH, follow: https://github.com/codekiddy2/Visual-Studio-gtkmm/blob/msvc-140/readme/path.md
7- If you did everything right the project should build now and you should see something like this if you run some boilerplate code for gtkmm http://puu.sh/pV2l2/f11eed1664.png
