bugfix: h5write size type

Some functions may pass a non-double size to h5write, which matlab needs, despite the data inherently being integer.
This casts size to double.

emptyness passthrough

the non-writing functions now return empty-like values when empty filename or other parameters are passed in. This seems to be a better match to expected behavior of other Matlab functions: empty in, empty out.

• {h5,nc}exist
• {h5,nc}size
• {h5,nc}variables

Separately, we moved CI to Azure since Travis-CI now has quotas, even for open-source projects.

add numerous tests

go to Class-based unit tests and use parameterization to find more corner cases

add lint tests

make internal functions private

this helps in reusing this code in external projects

re-enable HDF5 string, enhance test coverage

HDF5 can read and write strings again.

Add more type tests and coverage

use function-based tests

improve code test quality by using function-based tests

CI: add Matlab Travis-CI

v3.0.1

use string.empty

use R2019b argument validation

Improve reliability, discover and fix bugs by using R2019b argument validation and strings

use name,value options for less common options in {h5,nc}save

package layout for reliability

v2.0.0

ci

zenodo doi

No change, enabling zenodo doi