Update README.md

Author: tdicola

README.md

@@ -1,2 +1,18 @@
-# Adafruit_Python_LSM303
+# Adafruit Python LSM303
 Python code to use the LSM303 accelerometer & magnetometer with Raspberry Pi & BeagleBone Black.
+
+## Installation
+
+To install the library from source (recommended) run the following commands on a Raspberry Pi or other Debian-based OS system:
+
+    sudo apt-get install git build-essential python-dev
+    cd ~
+    git clone https://github.com/adafruit/Adafruit_Python_LSM303.git
+    cd Adafruit_Python_LSM303
+    sudo python setup.py install
+
+Alternatively you can install from pip with:
+
+    sudo pip install adafruit-lsm303
+
+Note that the pip install method **won't** install the example code.