! improves .travis.yml

- add pip cache
- move 'git status' to after_script

.travis.yml

 language: java
+# Building a Java project
+#   https://docs.travis-ci.com/user/languages/java
+#
 # how to install and set jdk on travis:
 # - Testing Against Multiple JDKs
 #   https://docs.travis-ci.com/user/languages/java/#Testing-Against-Multiple-JDKs
@@ -8,6 +11,7 @@ language: java
 #   https://docs.travis-ci.com/user/customizing-the-build/#Build-Matrix
 
 dist: trusty
+
 addons:
   apt:
     packages:
@@ -17,6 +21,9 @@ branches:
   except:
     - appveyor
 
+# Job Lifecycle
+#   https://docs.travis-ci.com/user/job-lifecycle/
+
 before_install:
   # workaround for "buffer overflow detected" problem of openjdk:
   #     https://github.com/travis-ci/travis-ci/issues/5227
@@ -41,15 +48,18 @@ script:
 after_success:
   # codecov
   - ./scripts/codecov.sh
+
+after_script:
   - git status --ignored
 
+before_cache:
+  # clear TTL maven self install
+  - rm -rf $HOME/.m2/repository/com/alibaba/transmittable-thread-local
 # Caching Dependencies and Directories
 # https://docs.travis-ci.com/user/caching/
 cache:
-  directories:
+  - pip
+  - directories:
     - $HOME/.m2
     - $HOME/.sdkman
     - $HOME/.cache/pip
-before_cache:
-  # clear TTL maven self install
-  - rm -rf $HOME/.m2/repository/com/alibaba/transmittable-thread-local