Update huxley screenshots

Update huxley, and then use the Dockerfile to create new huxley screenshots.

Test plan:
 - Make sure generating new huxley screenshots works
 - Ensure that re-generating huxley screenshots produces no changes

Auditors: alpert

dockers/HuxleyTests/Dockerfile

@@ -10,4 +10,4 @@ RUN echo "java -jar /selenium-server-standalone-2.42.2.jar > /dev/null &" >> ~/r
 RUN echo "Xvfb :1 2> /dev/null &" >> ~/run.sh
 RUN echo "make -C /KaTeX serve > /dev/null &" >> ~/run.sh
 RUN echo "sleep 2" >> ~/run.sh
-RUN echo "/KaTeX/node_modules/.bin/hux --update /KaTeX/test/huxley/" >> ~/run.sh
+RUN echo "/KaTeX/node_modules/.bin/hux --write /KaTeX/test/huxley/" >> ~/run.sh

package.json

@@ -19,7 +19,7 @@
         "less": "~1.4.2",
         "uglify-js": "~2.4.15",
         "clean-css": "~2.2.15",
-        "huxley": "~0.7.4",
+        "huxley": "~0.8.1",
         "jasmine-node": "git://github.com/mhevery/jasmine-node.git#Jasmine2.0"
     },
     "bin": "cli.js",