Added libjansson-dev to Travis.

.travis.yml

@@ -4,6 +4,9 @@ before_script:
   - _libsodium_version=0.7.0
   - _weechat_version=v1.0
 
+    # install libjansson
+    sudo apt-get install libjansson-dev
+
     # install libsodium (needed for libtoxcore)
   - git clone git://github.com/jedisct1/libsodium.git > /dev/null
   - pushd libsodium