Extend Travis definition file

Test with more D compilers and versions, and test building with Meson as
well.

.travis.yml

@@ -1,2 +1,33 @@
-language: d
+dist: trusty
 sudo: false
+
+language: d
+os:
+ - linux
+ - osx
+d:
+ - dmd
+ - dmd-beta
+ - dmd-nightly
+ - ldc
+ - ldc-beta
+
+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