see if upgrade to 1.18 fixes gpgme build failure.

Author: rouilj

.travis.yml

@@ -105,7 +105,7 @@ before_install:
   - make && make install
 
   # gpgme
-  - GPGME_VERSION=1.17.1
+  - GPGME_VERSION=1.18
   - cd /tmp
   - curl -s -O https://www.gnupg.org/ftp/gcrypt/gpgme/gpgme-$GPGME_VERSION.tar.bz2
   - tar -jxf gpgme-$GPGME_VERSION.tar.bz2