Only build master and PRs, not branches *and* their PRs.

Author: chriskrycho

.travis.yml

@@ -35,3 +35,8 @@ script:
   # Usually, it's ok to finish the test scenario without reverting
   #  to the addon's original dependency state, skipping "cleanup".
   - node_modules/.bin/ember try:one $EMBER_TRY_SCENARIO test --skip-cleanup
+
+# We build PRs, but don't trigger separate builds for the PR from the branch.
+branches:
+  only:
+    - master

appveyor.yml

@@ -37,3 +37,8 @@ build: off
 
 # Set build version format here instead of in the admin panel.
 version: "{build}"
+
+# We build PRs, but don't trigger separate builds for the PR from the branch.
+branches:
+  only:
+    - master