Susy-cross-section

This release breaks backward compatibility.

Major features

- refactor all modules with extended docstrings.
- change `.info` file format (and hopefully finalized).
- provide [HTML](https://susy-cross-section.readthedocs.io/) and PDF documents (PDF is not build yet).

Debugs

- fix Unit routines

Notes

For compatiblility with [Black format](https://black.readthedocs.io/en/stable/), line-length is modified to 88 characters for codes and 79 characters for docstrings.

Major features

- `susy-xs-get [TABLE]` now handles multi-dimensional linear fitting (4).
- `susy-xs-get [TABLE]` with no parameters now displays the information of Cross Section Table and detailed usage.
- `susy-xs-show` displays the table itself (mainly as a helper to write `info` file).

Internal features

- feat: use granularity to normalize cross-section data grid
- feat: add validations of cross-section data grid
- refactor: rewrite axes wrapper for multiindex compatibility
- refactor: rewrite interpolators in consistent manner
- feat: add RegularGridInterpolator for MultiIndex data
- feat: change API interpolator.interpolate to accept CrossSectionTable
- feat: improve 1d spline interpolation
- feat: modify Grid interpolator API


Minor debugs

- debug: use builtin method to get dimension of index

New data

- data: add some of FastLim 8TeV cross-section tables

TODOs

- more reasonable and helpful Error handling

Features
- supports Python 2.7
- integrates with Travis-CI and coveralls.io

Chore
- amend readme

The initial version of this handler package.

Features

- using as a python3 package will work totally fine.
- `susy-xs-get 13TeV.n2x1+.wino 777` will work and give 777-GeV wino cross-section (in python3).

TODO

- Python2 support
- tests with CI
- more data table
- multi-dimensional interpolation
- more-customized interpolator

Database with JSON format.