doc and readme

rpi/README.md

@@ -51,6 +51,13 @@ pacman -S python
 git clone https://aur.archlinux.org/python-smbus.git
 cd python-smbus
 makepkg -sri
+
+#pip
+pacman -S python-pip
+
+#nmea
+pip install pynmea2
+
 ```