Visual file diffs not rendering correctly
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### Description

Image diffs not rendering accurately.

### Version



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**Kactus version:** 0.1.6

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**OS version:** 10.12.5

### Steps to Reproduce

1. Create a sketch file from the Kactus app
2 . Save file in Sketch app
3. Alter Sketch file and save again
4. Click on changed file in Kactus
5. Only one file is shown w/wrong colors and the 2-up, swipe, onion skin, and difference are not selectable

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**Expected behavior:** I expected to see the old file and new file correctly rendered in Kactus.

**Actual behavior:** I saw the most recent file only and the colors are not correct.

**Reproduces how often:** 100%

### Logs

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#### Additional Information

Original in Sketch:

https://www.dropbox.com/s/lxuc1b4wft2mzwa/Screenshot%202017-07-17%2012.07.42.png?dl=0

Kactus Diff

https://www.dropbox.com/s/cmj10a0h0zc2vje/Screenshot%202017-07-17%2012.07.30.png?dl=0

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