add usage to README

README.md

@@ -1,47 +1,38 @@
-ScreenCalc
-======
-A simple screen size calculator
+# ScreenCalc
+A simple screen size calculator to convert screen measurement units at various
+densities
 
-[![Build Status](http://img.shields.io/travis/joshfriend/dpi-converter/master.svg)](https://travis-ci.org/joshfriend/dpi-converter)
-[![Coverage Status](http://img.shields.io/coveralls/joshfriend/dpi-converter/master.svg)](https://coveralls.io/r/joshfriend/dpi-converter)
+[![Build Status](http://img.shields.io/travis/joshfriend/screencalc/master.svg)](https://travis-ci.org/joshfriend/screencalc)
+[![Coverage Status](http://img.shields.io/coveralls/joshfriend/screencalc/master.svg)](https://coveralls.io/r/joshfriend/screencalc)
 [![PyPI Version](http://img.shields.io/pypi/v/ScreenCalc.svg)](https://pypi.python.org/pypi/ScreenCalc)
 [![PyPI Downloads](http://img.shields.io/pypi/dm/ScreenCalc.svg)](https://pypi.python.org/pypi/ScreenCalc)
 
+# Getting Started
 
-Getting Started
-===============
-
-Requirements
-------------
-
-* Python 2.7+ or Python 3.3+
-
-Installation
-------------
-
-ScreenCalc can be installed with pip:
-
+Install:
 ```
 $ pip install ScreenCalc
 ```
 
-or directly from the source code:
-
-```
-$ git clone https://github.com/joshfriend/dpi-converter.git
-$ cd dpi-converter
-$ python setup.py install
-```
-
-Basic Usage
-===========
-
-After installation, the package can imported:
-
+Use it:
 ```
-$ python
->>> import sc
->>> sc.__version__
+$ sc 100px@hdpi 100dp ...
+100.0px@240dpi
++-----------+---------+----------+---------+---------+----------+------+
+| density   |      dp |       px |      sp |      mm |       in |   pt |
+|-----------+---------+----------+---------+---------+----------+------|
+| ldpi      | 66.6667 |  50      | 66.6667 | 10.5833 | 0.416667 |   30 |
+| mdpi      | 66.6667 |  66.6667 | 66.6667 | 10.5833 | 0.416667 |   30 |
+| tvdpi     | 66.6667 |  88.75   | 66.6667 | 10.5833 | 0.416667 |   30 |
+| hdpi      | 66.6667 | 100      | 66.6667 | 10.5833 | 0.416667 |   30 |
+| xhdpi     | 66.6667 | 133.333  | 66.6667 | 10.5833 | 0.416667 |   30 |
+| xxhdpi    | 66.6667 | 200      | 66.6667 | 10.5833 | 0.416667 |   30 |
+| xxxhdpi   | 66.6667 | 266.667  | 66.6667 | 10.5833 | 0.416667 |   30 |
++-----------+---------+----------+---------+---------+----------+------+
+
+...
 ```
 
-ScreenCalc doesn't do anything, it's a template.
+Known measurement units are: `dp`, `px`, `sp`, `mm`, `in`, and `pt`. Screen
+density can be one of the named values (`ldpi`, `mdpi`, `tvdpi`, `hdpi`,
+`xhdpi`, `xxhdpi`, or `xxxhdpi`), or a decimal value (e.g. `100`).