deposit: Flask-WTF update to 0.9.5

Travis is failing because WTForms got bumped to 2.0
```
File "/home/travis/virtualenv/python2.7.6/lib/python2.7/site-packages/invenio/modules/deposit/fields/__init__.py", line 20, in <module>

from wtforms.fields.core import _unset_value

ImportError: import_string() failed for 'invenio.modules.annotations.views'.
...
ImportError: cannot import name _unset_value
```