Added simple install guide

Author: mbartling

tools/bash_completion/install.md

@@ -0,0 +1,13 @@
+# Install Guide
+
+## System-wide Installation (root)
+
+- Copy or link the bash completion script, `mbed`,  into your `/etc/bash_completion.d` or `/usr/local/etc/bash_completion.d` directory.
+- Reopen terminal
+
+## Local Installation
+
+- `mkdir ~/.bash_completion.d && cp mbed ~/.bash_completion.d/`
+- `echo "source ~/.bash_completion.d/mbed" >> ~/.bash_profile`
+- logout and login
+