Release v0.9.1

New:

• mbed CLI will attempt to auto-install Python dependencies. On failure it will show a warning with instructions how to install dependencies manually. Commands compile, test, export and detect now trigger Python dependencies auto-install.
• mbed config -L/--list to list global and local tool configuration (+ help and documentation)
• mbed compile and mbed test now support -o/--options (+ help and documentation)
• Fetch Git tags during mbed update
• Support requirements.txt in the mbed-os tools directory
• Add message when there's nothing to publish

Changes:

• --mcu is renamed to --target