update vexflow to 3.0.4, fixing many layout problems in 3.0.3 (#706)

some changes from 1.2.90 to 3.0.4 may be slightly worse, e.g. function test tabulature,
but overall, the benefits far outweigh.

package.json

@@ -67,7 +67,7 @@
     "loglevel": "^1.6.8",
     "svg2pdf.js": "^1.5.0",
     "typescript-collections": "^1.3.3",
-    "vexflow": "3.0.3"
+    "vexflow": "3.0.4"
   },
   "devDependencies": {
     "@types/chai": "^4.2.11",