Revert "ext: flask 0.11 fix"
Revert "ext: flask 0.11 fix"

* Reverts commit 93b3ce2413b5848ca66b01dad047cd74f1b46efb. The change
  broke Flask 0.10 installations.

Signed-off-by: Lars Holm Nielsen <7eaffca9f7cd98839b5821d0d23e09ff764b82cd@cern.ch>

inveniosoftware/invenio-theme,inveniosoftware/invenio-theme,inveniosoftware/invenio-theme,inveniosoftware/invenio-theme