ci: Run source clear only on cron and before linting and tests (#283)

Author: oakbani

.travis.yml

@@ -5,13 +5,13 @@ git:
 install:
   - eval "$(gimme)"
 stages:
+  - 'Source clear'
   - 'Lint markdown files'
   - 'Lint'
   - 'Unit test'
   - 'Benchmark test'  
   - 'Integration tests'
   - 'Production tests'
-  - 'Source clear'
   - 'Readme-sync'
 jobs:
   include:
@@ -87,6 +87,7 @@ jobs:
         FULLSTACK_TEST_REPO=ProdTesting
 
     - stage: 'Source clear'
+      if: type = cron
       env: GIMME_GO_VERSION=master GIMME_OS=linux GIMME_ARCH=amd64
       language: go
       addons: