Update Documentation + Create a Subproject for Important Markdown Docs (#451)

* add docs folder for markdowns

* create scripts project, move readmes

* update all docs

* fix travis

.travis.yml

@@ -14,7 +14,7 @@ matrix:
       env:
         - coverage
       script:
-        - ./coverage.sh
+        - ./scripts/coverage.sh
         - bash <(curl -s https://codecov.io/bash)
     - os: linux
       env: V=0.15.0
@@ -72,10 +72,10 @@ matrix:
             //... $REMOTE_FLAGS
         
         # Check that BUILD files are formatted correctly.
-        - ./check_gazelle.sh
+        - ./scripts/check_gazelle.sh
 
         # Check that target visibility is correct.
-        - ./check_visibility.sh
+        - ./scripts/check_visibility.sh
 
         # Shutdown must be last.
         - bazel shutdown