Update .gitignore (#73)

* Delete .DS_Store

* Update .gitignore w/ common exclusions

From https://github.com/github/gitignore/blob/master/Go.gitignore

.gitignore

@@ -1 +1,18 @@
+# Binaries for programs and plugins
+*.exe
+*.dll
+*.so
+*.dylib
+
+# Test binary, build with `go test -c`
+*.test
+
+# Output of the go coverage tool, specifically when used with LiteIDE
+*.out
+
+# Project-local glide cache, RE: https://github.com/Masterminds/glide/issues/736
+.glide/
+
+# Other
 .vscode
+.DS_Store