Fix path to downlaod cmake 3.17.5 (#299)

I updated this incorrectly on my last commit.

Author: bartlettroscoe

.travis.yml

@@ -5,7 +5,7 @@ dist: trusty
 
 before_install:
   - sudo apt-get update -qq
-  - wget -O cmake.sh https://cmake.org/files/v3.17.5/cmake-3.17.5-Linux-x86_64.sh
+  - wget -O cmake.sh https://cmake.org/files/v3.17/cmake-3.17.5-Linux-x86_64.sh
   - sudo mkdir /usr/local/cmake-3.17.5
   - sudo sh cmake.sh --skip-license --exclude-subdir --prefix=/usr/local/cmake-3.17.5
   - export PATH=/usr/local/cmake-3.17.5/bin:$PATH