Modify travis not to use pip in test.sh

Author: kngwyu

.travis.yml

@@ -33,7 +33,7 @@ before_install:
   - source ./ci/travis/setup.sh
 
 install:
-  - pip install setuptools-rust
+  - pip install -r ./example/requirements.txt
 
 script:
   - ./ci/travis/test.sh

ci/travis/test.sh

@@ -6,6 +6,5 @@ cargo build --verbose --all
 cargo test --verbose --all
 
 cd example
-pip install -r requirements.txt
 python setup.py develop
 ./test.py