Bump gscan to tarball link

no issue

- GScan 2.0 is in progress
- it's helpful to use a latest tarball already for testing
- https://github.com/TryGhost/gscan/commits/2.0

package.json

@@ -58,7 +58,7 @@
     "ghost-storage-base": "0.0.3",
     "glob": "5.0.15",
     "got": "7.1.0",
-    "gscan": "https://github.com/TryGhost/gscan/tarball/437c99f72cd6c350ffe1388f2a95a405637592cf",
+    "gscan": "https://github.com/TryGhost/gscan/tarball/058e4d63f254df0920f1b257a4992acfed13a476",
     "html-to-text": "3.3.0",
     "image-size": "0.6.3",
     "intl": "1.2.5",

yarn.lock

@@ -2551,9 +2551,9 @@ grunt@~0.4.0:
     underscore.string "~2.2.1"
     which "~1.0.5"
 
-"gscan@https://github.com/TryGhost/gscan/tarball/437c99f72cd6c350ffe1388f2a95a405637592cf":
+"gscan@https://github.com/TryGhost/gscan/tarball/058e4d63f254df0920f1b257a4992acfed13a476":
   version "1.5.1"
-  resolved "https://github.com/TryGhost/gscan/tarball/437c99f72cd6c350ffe1388f2a95a405637592cf#acc0964bd2a50634a41a64870ee9cb730a6c8c4a"
+  resolved "https://github.com/TryGhost/gscan/tarball/058e4d63f254df0920f1b257a4992acfed13a476#1bae864f251f2b3b4ffaf68958c0d75d322f103e"
   dependencies:
     "@tryghost/extract-zip" "1.6.6"
     bluebird "^3.4.6"