Add Back Image Handling

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Supercedes #5, #28, #33, #34, #56, #48

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Upon further investigation, in the live version, things seem to work for the most part. The butterfly example is broken. Fixing it shouldn't be too hard.

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I've thought of a good way to do this. Make the user input the number of rows and cols in the wordsearch. Ask them to click the four corners of the puzzle. This should support skewing. Take the nearest letter at each intersection. The hardest part about this will probably be handling intricacies of canvas (sizing). I don't like the existing canvas abstractions for react and will probably roll my own.

Some useful links:

• https://www.html5rocks.com/en/tutorials/canvas/hidpi/