Adding libunwind8 to .travis.yml

[skip appveyor]

Author: Nate McMaster

.travis.yml

@@ -10,6 +10,10 @@ os:
   - linux
   - osx
 osx_image: xcode8.2
+addons:
+  apt:
+    packages:
+      - libunwind8
 before_install:
   - if test "$TRAVIS_OS_NAME" == "osx"; then brew update; brew install openssl nginx; ln -s /usr/local/opt/openssl/lib/libcrypto.1.0.0.dylib /usr/local/lib/; ln -s /usr/local/opt/openssl/lib/libssl.1.0.0.dylib /usr/local/lib/; else ./install-nginx.sh; fi
 install: