Run brew update before brew install on Travis CI

Author: PeterDaveHello

.travis.yml

@@ -81,7 +81,7 @@ jobs:
     env:
       - task=test-dist-zsh
     before_script:
-      - brew install zsh
+      - brew update && brew install zsh
       - type zsh && zsh --version
     script:
       - ./test-scripts/zsh
@@ -90,7 +90,7 @@ jobs:
     env:
       - task=test-dist-ksh
     before_script:
-      - brew install ksh
+      - brew update && brew install ksh
       - type ksh && ksh --version || printf ""
     script:
       - ./test-scripts/ksh
@@ -107,7 +107,7 @@ jobs:
     env:
       - task=test-dist-bash-brew-install
     before_script:
-      - brew install bash
+      - brew update && brew install bash
       - export PATH="/usr/local/bin:$PATH"
       - type bash && bash --version
     script:
@@ -117,7 +117,7 @@ jobs:
     env:
       - task=test-dist-fish
     before_script:
-      - brew install fish
+      - brew update && brew install fish
       - type fish && fish --version
     script:
       - ./test-scripts/fish