[travis] Install wkhtmltopdf

.travis.yml

@@ -14,6 +14,9 @@ install:
   - sudo apt-get update
   - sudo apt-get purge -y mysql-common
   - sudo apt-get install mariadb-server mariadb-common libmariadbclient-dev
+  - wget http://downloads.sourceforge.net/project/wkhtmltopdf/0.12.1/wkhtmltox-0.12.1_linux-precise-amd64.deb
+  - sudo dpkg -i wkhtmltox-0.12.1_linux-precise-amd64.deb
+
   - CFLAGS=-O0 pip install git+https://github.com/frappe/frappe.git@$develop &&
   - pip install --editable .