attempt to make travis OSX tests green and mandatory

.travis.yml

@@ -5,20 +5,17 @@ os:
   - osx
 dist: trusty
 
-matrix:
-  allow_failures:
-    - os: osx
-
 addons:
   apt:
     packages:
     - libcurl4-openssl-dev
     - libsdl1.2-dev
     - libgc-dev
-  brew:
-    packages:
-    - boehmgc
-    - node
+
+before_install:
+  - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew update          ; fi
+  - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew install boehmgc; fi
+  - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew install node; fi
 
 before_script:
   - set -e
@@ -42,4 +39,3 @@ script:
   - nim c --taintMode:on -d:nimCoroutines tests/testament/tester
   - tests/testament/tester --pedantic all -d:nimCoroutines
   - ./koch csource
-  - ./koch xz