Theme Bootstrapping and fixes upload bug

Features:

You can now bootstrap a new theme onto a Shopify store using Timber. At the moment it requires that you have a pre-existing configuration in the directory.

For example, if you wanted to start a new theme based on the latest master you could do the following:

mkdir my_timber_theme
cd my_timber_theme
theme configure -access_token=abracadabra -domain=someshop.myshopify.com
theme bootstrap -version=master

Theme versions are pulled down from the Timber releases atom feed, so you never need to worry about using an out of date Timber theme (unless you want to).

Bugfixes:

• #31: Larger files not getting buffered correctly, resulting in broken uploads during theme watch