update README with test info
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README.md
README.md
-# Adafruit_Learning_System_Guides
-Smaller programs and scripts to display "inline" in Adafruit Learning System guides
+![build status](https://travis-ci.com/adafruit/Adafruit_Learning_System_Guides.svg?branch=master "Build Status")
+
+# Introduction
+
+This is a collection of smaller programs and scripts to display "inline" in
+[Adafruit Learning System][learn] guides. Subdirectories here will generally
+contain a README with a link to their corresponding guide.
+
+## Testing
+
+The code here is partially [checked by Travis CI][travis] against Pylint (for
+CircuitPython code) or the Arduino compilation process using
+[travis-ci-arduino][travis-ci-arduino].
+
+Code in directories containing a file called `.circuitpython.skip` will be
+skipped by Pylint checks.
+
+Code in directories containing a `.[platformname].test` file, such as
+`.uno.test` will be compiled against the corresponding platform.
+
+This is a work in progress.
+
+[learn]: https://learn.adafruit.com/
+[travis]: https://travis-ci.com/adafruit/Adafruit_Learning_System_Guides/
+[travis-ci-arduino]: https://github.com/adafruit/travis-ci-arduino/

update README with test info