Webpack dev server (#902)

* Initial webpack config. Moving to ES6 modules. Some module cleanup.

* WIP

* WIP

* Removing commented out code.

* Removing old deps.

* Removing the build script (used for testing).

* Working tests.

* Switching to node api over cli.

* Updating per comments. Still need to fix server.js to properly run the selenium tests.

* Cleaning up the config.

* More cleanup.

* Bringing back server.js for selenium tests.

* Bringing back old dependencies.

* Adding back eslint rules for webpack config. Final cleanup for webpack config.

* Pointing to correct pre-existing module versions. Adding some extra logic to server.js to ensure it gets transpiled properly.

* Getting make build to work again. Updating package.json with some shortcut scripts.

* Resolving conflict.

* Reverting back to commonjs modules.

* Removing extra spaces in babelrc

src/functions/delimsizing.js

@@ -1,5 +1,5 @@
 // @flow
-import buildCommon, {makeSpan} from "../buildCommon";
+import buildCommon from "../buildCommon";
 import defineFunction from "../defineFunction";
 import delimiter from "../delimiter";
 import mathMLTree from "../mathMLTree";
@@ -85,7 +85,7 @@ defineFunction({
         if (delim === ".") {
             // Empty delimiters still count as elements, even though they don't
             // show anything.
-            return makeSpan([group.value.mclass]);
+            return buildCommon.makeSpan([group.value.mclass]);
         }
 
         // Use delimiter.sizedDelim to generate the delimiter.
@@ -203,7 +203,7 @@ defineFunction({
         // Add it to the end of the expression.
         inner.push(rightDelim);
 
-        return makeSpan(["minner"], inner, options);
+        return buildCommon.makeSpan(["minner"], inner, options);
     },
     mathmlBuilder: (group, options) => {
         const inner = mml.buildExpression(group.value.body, options);