Mitch Garnaat

Adding a README to describe how to install nodejs dependencies for the S3 sample. Fixes #18.

This example requires some additionaly nodejs packages to be incuded in the zip
file that is uploaded to AWS.
To install these, first make sure you have nodejs installed locally. Then:
1. cd examplefolder
2. npm install async gm
This will create a node_modules directory under examplefolder and the required
nodejs packages will be included within that directory.
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