* MAINT: Post 0.11.1 release, drop py2, qt4
This focuses on distribution, tests, and docs. This may not be comprehensive, but covers the cases I found by looking and a few greps
Noteably, this does not change any actual internal code yet, to avoid merge conflicts with pending PRs.
* NEP 29 language/versions
* Handle axis SI prefix scaling in MatplotlibExporter
* Added some MatplotlibExporter tests and added matplotlib to CI deps
* Install mpl with pip instead of conda
* Cleanup
* HDF5Exporter handles ragged curves by saving them into different datasets based on their names.
* Add HDF5Exporter tests
* Document HDF5Exporter
* Fix tmp file path
* [skip-ci] Initial Azure-Pipelines configuration.
The following configurations are tested
* macOS 10.13
* ubuntu 16.04
* Windows Server 2016
Under each operating system, the following Qt bindings are tested
* conda based pyqt4
* conda based pyside
* conda based pyside2 (5.6)
* conda based PyQt5 (5.9)
* pip basedd PyQt5 (5.12)
* pip based PySide2 (5.12)
For each configuration, it runs `python -m pytest --cov pyqtgraph -sv`
The only configuration that actually passes all tests is Ubuntu-pip-PyQt5