Fix suggested gas price in trasaction for ui production build (#222)

* use string version of bignumber when converting gasPrice to hex
* update chromedriver version

ui-e2e/package.json

@@ -4,9 +4,9 @@
   "license": "MIT",
   "private": true,
   "devDependencies": {
-    "selenium-webdriver": "3.6.0",
+    "chromedriver": "^77.0.0",
     "mocha": "^5.2.0",
-    "chromedriver": "76.0.0"
+    "selenium-webdriver": "3.6.0"
   },
   "scripts": {
     "lint": "eslint . --ignore-path ../.eslintignore"

ui/src/stores/GasPriceStore.js

@@ -60,7 +60,7 @@ class GasPriceStore {
 
   @computed
   get gasPriceInHex() {
-    return toHex(this.gasPrice)
+    return toHex(this.gasPrice.toString())
   }
 }