Pandalone

------------------------------------------------------------------
- Fix xleash for pandas 0.25+ (19-July 2019).
- Fix *asteval* *xleash* filter to work correctly with latest version
using `usersym` table for context-variables (were missing those);
relax *asteval* version lower-bound < 0.9.10, but bump dependency
from ``>= 0.9.7 --> 0.9.8``.
- Fix 13: ``ensure_filename()`` util were duping filename's file-extension
if was given the same.
- Fix missing test-deps `ddt` & `openpyxl`.
- Fix git ignores.

------------------------------------
- fix: remove stray sources from xleash
(`xleash.io._xlwings` has syntax-errors irritating linters)
- feat: backport build/bumpver scripts from v0.3.x
(above bug was a results of a bad build).

-----------------------------------
- build:
- drop dep-tricks for older Pythons & correct old missconceptions.
- drop never used `openpyxl` dep
- drop `sphinx_rtd_theme` not-really-needed-these-days dep

--------------------
- Fix py36 "nested regex" warning on ``xleash._parse`` module.
- Pin ``jsonschema <3`` since `_types` has been dropped.
- Updates to `setup.py`, dependencies & build-scripts.
- VSCode files & dev plugins.

--------------------------
Released just to move ``easygui`` dependency to (renamed from ``xlwings``-->)
`[excel]` extras, just for co2mpas summer release.

- ``v0.2.4.post1`` had unwanted WIPs.

---------------------------------------
- fix(xleash.io, 12): sheet margins failed with > 32bit num of rows/cols