Have Travis test Meson builds as well

This is a relatively easy way to have working Meson builds without the
need for sudo or Docker in Travis.

.travis.yml

@@ -1,4 +1,6 @@
 language: d
+dist: trusty
+sudo: false
 
 os:
   - linux
@@ -8,4 +10,23 @@ d:
   - dmd
   - ldc
 
-sudo: false
+
+before_install:
+  - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew update; fi
+  - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew install ninja python3; fi
+  - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then pip3 install meson; fi
+  - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then pip3 install meson; fi
+
+install:
+  - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then mkdir .ntmp && curl -L https://github.com/ninja-build/ninja/releases/download/v1.7.2/ninja-linux.zip -o .ntmp/ninja-linux.zip; fi
+  - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then unzip .ntmp/ninja-linux.zip -d .ntmp; fi
+
+before_script:
+  - export PATH=$PATH:$PWD/.ntmp
+
+script:
+  - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then meson build && ninja -C build; fi
+  - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then ninja -C build test -v; fi
+  - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then SDKROOT=$(xcodebuild -version -sdk macosx Path) meson build && ninja -C build test; fi
+  - dub build
+  - dub test