Try fix ta-lib install

.travis.yml

@@ -17,7 +17,7 @@ addons:
     - libdw-dev
     - binutils-dev
 install:
-- ./build_helpers/install_ta-lib.sh
+- cd build_helpers && ./install_ta-lib.sh
 - export LD_LIBRARY_PATH=/usr/local/lib:$LD_LIBRARY_PATH
 - pip install --upgrade flake8 coveralls pytest-random-order pytest-asyncio mypy
 - pip install -r requirements-dev.txt

build_helpers/install_ta-lib.sh

@@ -1,5 +1,5 @@
 if [ ! -f "ta-lib/CHANGELOG.TXT" ]; then
-  tar zxvf build_helpers/ta-lib-0.4.0-src.tar.gz
+  tar zxvf ta-lib-0.4.0-src.tar.gz
   cd ta-lib \
   && sed -i.bak "s|0.00000001|0.000000000000000001 |g" src/ta_func/ta_utility.h \
   && ./configure \