Update README.md

Adds an image.
Simple ahead download #9
#11 very rough impl for pinch to zoom a page.
Keep the current page for a book iOS #14
Listens to application lifecycle #14
resolves #3, touched #22.
resolves #21
Script to decompose PDF to jpgs, resolves #7
svn checkout google-api-objectivec-client
Uses a proxy server and Google Drive for storage.
SQLite3 db schema.
Sever based on express.js
iPad app roughly works with Google Drive.
Moved iOS.
Renames server.
Cleans up DB.
Renames in pod.
Use GDrive identifier for cover image, since cached URL goes invalid afterwards.
Use cached image on view load.
pseudo code for handling book upload