Add basic README

Author: tomstokes

README.md

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+# python-spi
+
+**Note:** python-spi is still a work in progress.
+
+## Overview
+
+A pure Python SPI interface using the Linux spidev device
+
+## Features
+
+- Pure Python implementation. No C module to compile.
+- Supports half-duplex reads and writes as well as full-duplex transfers.
+- Exposes all available spidev interface options as properties.
+
+## Example
+
+    import spi
+    spi = SPI("/dev/spidev1.0")
+    spi.mode = SPI.MODE_0
+    spi.bits_per_word = 8
+    spi.speed = 500000
+    received = spi.transfer("\xAA\xBB\xCC")
+    spi.write("\x00\x11\x22")
+    received = spi.read(10)
+
+
+