Updated travis config to install exiftool

Author: Tom Van Herreweghe

.travis.yml

@@ -7,4 +7,9 @@ php:
 script: phpunit
 
 before_script:
-  - composer install --dev --prefer-source
+  - composer install --dev --prefer-source
+
+before_install:
+  - cd /tmp && wget http://www.sno.phy.queensu.ca/~phil/exiftool/Image-ExifTool-9.32.tar.gz
+  - tar -zxvf Image-ExifTool-9.32.tar.gz
+  - cd Image-ExifTool-9.32 && perl Makefile.PL && make test && sudo make install