added README

README.markdown

+## About the Book
+
+[*Exploring Android*](https://commonsware.com/AndExplore/)
+is an integrated set of tutorials, guiding you step-by-step in building an 
+Android application. 
+
+This book is updated a few times a year and is available through
+[the Warescription](https://commonsware.com/warescription) program. Subscribers also have access to office
+hours chats and other benefits.
+
+This repository contains the source code for the sample apps profiled in the book. These 
+samples are updated as the book is, with `git` tags applied to tie sample code versions to book
+versions.
+
+The book, and the samples, were written by Mark Murphy. You may also have run into him through
+Stack Overflow:
+
+<a href="http://stackoverflow.com/users/115145/commonsware">
+<img src="http://stackoverflow.com/users/flair/115145.png" width="208" height="58" alt="profile for CommonsWare at Stack Overflow, Q&amp;A for professional and enthusiast programmers" title="profile for CommonsWare at Stack Overflow, Q&amp;A for professional and enthusiast programmers">
+</a>
+
+All of the source code in this archive is licensed under the
+Apache 2.0 license except as noted.
+
+Each directory in this repository reflects the "answers" to having completed
+the tutorials to a certain point. So, for example, the `T11-Repository/`
+directory contains a copy of the app being built, after having completed the
+11th tutorial ("Setting Up a Repository"). If you wish to import
+the results of one of the tutorials into Android Studio, you want to import
+the `ToDo/` directory inside of one of the top-level directories. In other
+words, import `T11-Repository/ToDo/`, not `T11-Repository/`.
+
+Remember,
+**always check the `gradle-wrapper.properties` file before importing anything into Android Studio**,
+as there is always the chance that somebody has published material linking you to a hacked Gradle installation.
+