Add Ruby 2.7 to CI config & cross build list

Author: aharpervc

.travis.yml

@@ -11,6 +11,7 @@ rvm:
   - 2.4.5
   - 2.5.3
   - 2.6.1
+  - 2.7.0
 before_install:
   - docker info
   - sudo ./test/bin/install-openssl.sh

appveyor.yml

@@ -49,5 +49,7 @@ environment:
     - ruby_version: "25"
     - ruby_version: "26-x64"
     - ruby_version: "26"
+    - ruby_version: "27-x64"
+    - ruby_version: "27"
 on_failure:
   - find -name compile.log | xargs cat

tasks/native_gem.rake

@@ -8,7 +8,7 @@ task 'gem:windows' => ['ports:cross'] do
   build = ['bundle']
 
   # and finally build the native gem
-  build << 'rake cross native gem RUBY_CC_VERSION=2.6.0:2.5.0:2.4.0 CFLAGS="-Wall" MAKE="make -j`nproc`"'
+  build << 'rake cross native gem RUBY_CC_VERSION=2.7.0:2.6.0:2.5.0:2.4.0 CFLAGS="-Wall" MAKE="make -j`nproc`"'
 
   RakeCompilerDock.sh build.join(' && ')
 end