Removed Bison related settings from `.travis.yml` and `appveyor.yml`

.travis.yml

@@ -3,9 +3,6 @@ language: c
 jobs:
   - os: linux
   - os: osx
-    before_install:
-      - HOMEBREW_NO_AUTO_UPDATE=1 HOMEBREW_NO_INSTALL_CLEANUP=1 brew install bison
-      - export PATH="/usr/local/opt/bison/bin:$PATH"
 
 env:
   - MRUBY_CONFIG=travis_config.rb

appveyor.yml

@@ -4,11 +4,6 @@ os: Visual Studio 2017
 
 shallow_clone: true
 
-
-cache:
-  - win_flex_bison
-
-
 environment:
   matrix:
     # Visual Studio 2017 64bit
@@ -38,14 +33,7 @@ init:
   - ruby --version
 
 
-install:
-  - if not exist win_flex_bison (
-      appveyor DownloadFile "https://github.com/lexxmark/winflexbison/releases/download/v.2.5.10/win_flex_bison-2.5.10.zip" &
-      7z x -y -owin_flex_bison win_flex_bison-2.5.10.zip
-    )
-
 build_script:
-  - set YACC=.\win_flex_bison\win_bison.exe
   - set MRUBY_CONFIG=appveyor_config.rb
   - rake -m
   - rake -E $stdout.sync=true test