Changed minimum VS version to VS 2013 SP5 (#2610)

With this you will not be able to open the solution with any older visual studio version anymore.

rAthena.sln

@@ -2,7 +2,7 @@
 Microsoft Visual Studio Solution File, Format Version 12.00
 # Visual Studio 2013
 VisualStudioVersion = 12.0.40629.0
-MinimumVisualStudioVersion = 10.0.40219.1
+MinimumVisualStudioVersion = 12.0.40629.0
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "3rdparty", "3rdparty", "{6ABA1767-6242-4CA0-BA22-A30972DC8918}"
 EndProject
 Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "common", "src\common\common.vcxproj", "{F8FD7B1E-8E1C-4CC3-9CD1-2E28F77B6559}"