Fix OS X install problem

We patch the linkage manually anyway.  Skip over brew problems.

Author: snoe925

.travis.yml

@@ -8,7 +8,7 @@ os:
 
 before_install:
   - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew update; fi
-  - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew install tcl-tk; fi
+  - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew install tcl-tk || true; fi
   - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then mkdir -p /usr/local; ln -s /usr/local/opt/tcl-tk/include /usr/local/include/tcl8.6; fi
   - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then cp /usr/local/opt/tcl-tk/lib/libtcl* /usr/local/lib; fi
   - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then ln -s /usr/local/opt/tcl-tk/bin/tclsh8.6 /usr/local/bin/tclsh; fi