update CI config and pre-commit hook config (#228)

.pre-commit-config.yaml

@@ -26,3 +26,5 @@ repos:
     - id: double-quote-string-fixer
     - id: fix-encoding-pragma
       args: ["--remove"]
+    - id: mixed-line-ending
+      args: ["--fix=lf"]

.travis.yml

@@ -26,8 +26,8 @@ python:
 
 before_script:
   - pip install codecov flake8 yapf isort
-  - flake8
-  - isort -rc --diff mmcv/ tests/ examples/
+  - flake8 .
+  - isort -rc --check-only --diff mmcv/ tests/ examples/
   - yapf -r -d mmcv/ tests/ examples/
 
 script: coverage run --source=mmcv setup.py test