Develop method and scripts for running accuracy assessment

[apericak]

As we approach the end of #76 (manually classifying a bunch of points), we should start developing our method for actually conducting the accuracy assessment. We will, at a minimum, want to create confusion matrices per year, and probably some of the other scores discussed on this Wikipedia page..

Earth Engine does have built-in confusion matrix methods (see the ee.ConfusionMatrix tab in the Docs on the playground), so since we have so many points and so many years, we will likely want to write a new script to accomplish this.

[apericak]

For reference, here's what @cjthomas730 had accomplished as of 12 August 2016: https://code.earthengine.google.com/a6b45f1f4c067e1adcb8569bebb71350

[cjthomas730]

Here's the update as of 09/02: https://code.earthengine.google.com/e06d7ff71307408ddd952977a99d9972

[apericak]

This is addressed in #98, so once those changes are accepted we can close this issue (and thanks @cjthomas730 for researching and writing the code to make this accuracy assessment work!)