Fix URL for Tika download and add MD5 hash.

The download URL for tika 1.4 recently broke:
http://mirror.switch.ch/mirror/apache/dist/tika/tika-app-1.4.jar does not exist any more.
Because Switch removes old version quite aggressively, we replace the Tika download URL
with one pointing to https://archive.apache.org/dist/tika/ which should be much more stable.

Also verified that the MD5 sum of the archive from the new URL is the same as the old one
we used, and added that hash to the buildout.
/cc @phgross