Update main.workflow

Author: kenyonj

.github/main.workflow

@@ -1,17 +1,20 @@
 workflow "Test and build on push" {
-  resolves = [
-    "CI Test Runner",
-    "Jekyll Pages Builder",
-  ]
+  resolves = ["Jekyll Pages Builder"]
   on = "push"
 }
 
 action "CI Test Runner" {
+  needs = "checkout pull request"
   uses = "./.github/test_runner"
   secrets = ["GITHUB_TOKEN"]
 }
 
 action "Jekyll Pages Builder" {
+  needs = "CI Test Runner"
   uses = "./.github/pages_builder"
   secrets = ["GITHUB_TOKEN"]
 }
+
+action "checkout pull request" {
+  uses = "gr2m/git-checkout-pull-request-action@master"
+}