jenkins: Fix macOS build

Actions taken in this comment:
- Use latest version of macOS image
- Use latest conan version
- Update pip in the macOS builds

.travis.yml

@@ -69,9 +69,9 @@ matrix:
       env:
         - BUILD_TYPE="Debug"
 
-    - name: "OS X 10.13 - XCode 10.2"
+    - name: "macOS 10.14 - XCode 11.3"
       os: osx
-      osx_image: xcode10.2
+      osx_image: xcode11.3
       compiler: clang
       env:
         - BUILD_TYPE="Release"

ci/install.sh

@@ -20,10 +20,11 @@ else
     eval "$(pyenv virtualenv-init -)"
     pyenv virtualenv conan
     pyenv activate conan
+    python -m pip install --upgrade pip
 fi
 
 python --version
-pip install conan==1.19.1
+pip install conan==1.22.0
 pip install codecov
 conan --version
 conan config set storage.path=~/conanData