docs: note on golang-1.8-go bin path

The golang-1.8-go package puts binaries in /usr/lib/go-1.8/bin. A new user might find it confusing that go binary is missing in the path

docs/INSTALL.md

@@ -14,6 +14,7 @@
     ```
     sudo apt-get install golang-1.8-go
     ```
+    > Note that golang-1.8-go puts binaries in /usr/lib/go-1.8/bin. If you want them on your PATH, you need to make that change yourself.
 
     On Mac OS X
     ```