.vs/ and CmakeSettings.json to gitignore (#522)

.gitignore

diff --git a/.gitignore b/.gitignore
index bfc6b57..93d5ced 100644
--- a/.gitignore
+++ b/.gitignore
@@ -45,6 +45,9 @@
 build/
 _build/
 
-# in-source dependancies
+# in-source dependencies
 /googletest/
 
+# Visual Studio 2015/2017 cache/options directory
+.vs/
+CMakeSettings.json