Improve README (#15)

Add Usage, How does it work and contributing sections. Fixes #2

Author: xredo

README.md

@@ -1,2 +1,31 @@
-# pathfinder
-Rails Template for MarsBased projects
+# Pathfinder
+
+![Pathfinder](https://upload.wikimedia.org/wikipedia/commons/thumb/2/23/Mars_pathfinder_panorama_large.jpg/1200px-Mars_pathfinder_panorama_large.jpg)
+
+Rails Template for MarsBased projects.
+
+## Usage
+
+The recommended way to use it is referencing the template directly from the Github repository.
+
+```
+rails new new_app -m https://raw.githubusercontent.com/MarsBased/pathfinder/master/template.rb
+```
+
+## How does it work
+
+Usually, Rails templates are being built from a single template file. However, if you want to create more complex templates, managing everything this way is painful.
+
+For this reason, we have organized the project in several recipes that can be applied based on the user feedback.
+
+The template.rb file will first clone the whole Pathfinder repository into a temporary local folder and then will execute itself.
+
+## Contributing
+
+You just need to clone the repository
+
+```git clone git@github.com:MarsBased/pathfinder.git```
+
+make the desired changes and test it locally by using:
+
+```rails new new_app -m pathfinder_local_repo/template.rb```