updated README

Author: sommersoft

README.rst

@@ -10,6 +10,10 @@ Introduction
     :target: https://discord.gg/nBQh6qu
     :alt: Discord
 
+.. image:: https://travis-ci.org/adafruit/Adafruit_CircuitPython_Thermal_Printer.svg?branch=master
+    :target: https://travis-ci.org/adafruit/Adafruit_CircuitPython_Thermal_Printer
+    :alt: Build Status
+
 CircuitPython module for control of various small serial thermal printers.
 
 Dependencies
@@ -25,15 +29,7 @@ This is easily achieved by downloading
 Usage Example
 =============
 
-See examples/simpletest.py for a demo of basic printer usage.
-
-API Reference
-=============
-
-.. toctree::
-   :maxdepth: 2
-
-   api
+See examples/thermal_printer_simpletest.py for a demo of basic printer usage.
 
 Contributing
 ============
@@ -65,3 +61,26 @@ Then run the build:
 .. code-block:: shell
 
     circuitpython-build-bundles --filename_prefix adafruit_circuitpython_thermal_printer --library_location .
+
+Sphinx documentation
+-----------------------
+
+Sphinx is used to build the documentation based on rST files and comments in the code. First,
+install dependencies (feel free to reuse the virtual environment from above):
+
+.. code-block:: shell
+
+    python3 -m venv .env
+    source .env/bin/activate
+    pip install Sphinx sphinx-rtd-theme
+
+Now, once you have the virtual environment activated:
+
+.. code-block:: shell
+
+    cd docs
+    sphinx-build -E -W -b html . _build/html
+
+This will output the documentation to ``docs/_build/html``. Open the index.html in your browser to
+view them. It will also (due to -W) error out on any warning like Travis will. This is a good way to
+locally verify it will pass.