Support visual studio 2014

[GoogleCodeExporter]

What steps will reproduce the problem?
1. Specify msvs as generator with version 2014

What is the expected output? What do you see instead?
A valid 2014 sln file but instead an error is thrown. 

What version of the product are you using? On what operating system?
Visual studio 2014 on Windows 8.1

Original issue reported on code.google.com by peter.su...@gmail.com on 21 Aug 2014 at 5:42

[GoogleCodeExporter]

Here is a path to get this working: 
https://github.com/springmeyer/gyp/pull/1.diff.

In the meantime a hack that I've been using previously was to add 1) make sure 
all 2014 dev tools where on the PATH, 2) add`"msbuild_toolset":"v140"` to the 
target_defaults, and 3) tell the generator to generate a visual studio file for 
2013.

Original comment by d...@mapbox.com on 4 Nov 2014 at 3:50

[GoogleCodeExporter]

Anything I can do to help this along?

Original comment by d...@mapbox.com on 11 Nov 2014 at 6:10

[GoogleCodeExporter]

Anyone able to review my patch?

Original comment by d...@mapbox.com on 13 Nov 2014 at 7:46

[GoogleCodeExporter]

Looks like this is now done via the addition of 2015 
(https://code.google.com/p/gyp/source/detail?r=2013)

Original comment by d...@mapbox.com on 14 Jan 2015 at 4:10