added some docs to the README

README.rst

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+Bunker -- An encrypted data store for Python
+********************************************
+
+.. contents::
+
+Basic Design
+============
+
+``bunker`` is based on the excessive use of ``tarfile`` and
+AES encryption. ``bunker`` stores its data in bunker-files
+which are tar archives containing both some meta data
+(currently unencrypted, is on the TODO list) and encrypted
+files containing the actual data.
+
+Basic API
+=========
+
+The main class used for accessing data stored in the bunker
+file is the class ``bunker.bunker.Bunker``. It can be used
+to create new bunkers and open existing bunkers. Both is
+done using the classmethod
+``bunker.bunker.Bunker.open(path)``. One can then add new
+components (like a `Key Value Store`_) using the method
+``add_component`` that will return an open component of
+a given type.  Using the method ``get_component`` one can 
+open an existing component.
+
+The components bring various methods to modify the data,
+changes are written to the bunker by using either the method
+``component.write_back`` or ``component.close`` the latter
+will also bring the component in a state where it cannot be
+used anymore (and delete all sensitive data).
+
+``bunker.bunker.Bunker`` can also be used as a context. All
+open components will be closed automatically when the
+context is left, ensuring that no sensitive data is left on
+the disk/in memory.
+
+Supported Data Stores
+=====================
+
+Key Value Stores
+----------------
+
+One can store data in key value stores. Those are based on
+``ljson.slapdash`` tables and work with several data types.