global: release checklist
global: release checklist

* Adds changes according to the release preparation checklist.

* Removes RELEASE-NOTE.rst file.

* Removes pyPEG2 from setup.py (it seems to be a dependency of
  invenio-iquery-parser).

* Removes SEARCH_ALLOWED_KEYWORDS from config (no longer used).

* Removes walkers - they will be moved to invenio-query-parser.

Signed-off-by: Sebastian Witowski <139b56c0e02b2c22f4e756593dbc8e818fe05596@gmail.com>

inveniosoftware/invenio-search,tiborsimko/invenio-search,inveniosoftware/invenio-search,tiborsimko/invenio-search