update readme (#93)

Author: DannyBen

README.md

@@ -17,11 +17,52 @@ Create feature-rich bash scripts using simple YAML configuration
 
 </div>
 
+Bashly is a command line application (written in Ruby) that lets you
+generate feature-rich bash command line tools.
+
+Bashly lets you focus on your specific code, without worrying about command line
+argument parsing, usage texts, error messages and other functions that are
+usually handled by a framework in any other programming language.
+
+It is available both as a [ruby gem](https://rubygems.org/gems/bashly) and as
+a [docker image](https://hub.docker.com/r/dannyben/bashly).
+
+
 ## Documentation
 
 - [Bashly Homepage][docs]
 - [Examples][examples]
 
+## How it works
+
+1. You provide a YAML configuration file, describing commands, sub-commands,
+   arguments, and flags. Running `bashly init` creates an initial sample YAML
+   file for you ([example](https://github.com/DannyBen/bashly/tree/master/examples/minimal#bashlyyml)).
+2. Bashly then automatically generates a bash script (when you run
+   `bashly generate`) that can parse and validate user input, provide help
+   messages, and run your code for each command.
+3. Your code for each command is kept in a separate file, and can be merged
+   again if you change it.
+
+## Features
+
+Bashly is responsible for:
+
+- Generating a **single, standalone bash script**.
+- Generating **usage texts** and help screens, showing your tool's arguments, flags and commands (works for sub-commands also).
+- Parsing the user's command line and extracting:
+  - Optional or required **positional arguments**.
+  - Optional or required **option flags** (with or without flag arguments).
+  - **Commands** (and sub-commands).
+  - Standard flags (like **--help** and **--version**).
+- Preventing your script from running unless the command line is valid.
+- Providing you with a place to input your code for each of the functions your tool performs, and merging it back to the final script.
+- Providing you with additional (optional) framework-style, standard library functions:
+  - **Color output**.
+  - **Config file management** (INI format).
+  - **YAML parsing**.
+  - **Bash completions**.
+  - and more.
 
 ## Contributing / Support