Animatplot

This is a maintenance release to ensure everything works with newer versions of python. Bigger changes will come in 0.5.0.

The changelog needs to be updated for release.

- Improved Line Block input handling and testing
- Added title block
- Timeline_slider now defaults the format specifier valfmt to None. If set to None, it will use %1.2% for most cases, but %s for np.datetime.

Backwards incompatible changes:
- The x, y inputs to the Line Block are not positional only
- Removed axis kwargs that deprecated in favor of ax in 0.3.0

Dev changes:
- testing tools was moving into the tests folder and is no longer a subpackage of animatplot.
- CircleCI script was refactored

This release has multiple contributors (and the first release to have such):
t-makaro
TomNicholas*
dcherian*

*indicates new contributor.

Deprecations
- The axis keyword argument has been replaced (everywhere) in favour of ax, and axis will be removed completely in 0.4.0. This does not apply to t_axis which is unchanged. See 10 for rational.
Features
- The Pcolormesh block now accepts 1D arrays (in addition to 2D) for x and y inputs.
Animation.timeline_slider now accepts a text argument to change the name of the slider.
- New blocks:
- Scatter for animating scatter plots. Capable of animating size and position of the points, but not yet the color.
- Update a block that accepts a generic function that takes a frame number. Good if another block doesn’t already exist for some tasks.
- Composition Blocks: These are functions that return a list of blocks (and maybe a timeline). These are in the blocks subpackage and can be identified by the _comp suffix.
- New (and very experimental) animations subpackage (well new to the public api). Contains some new convenice functions.
- vector_plot wraps Pcolormesh and Quiver to produce animated vector fields.
Bug Fixes
- Previously, an Animation with a timeline_slider, but no toggle would cause an error.
Breaking Changes
- The text argument to timeline_slider is now the first positional argument.
- The order of positional arguments for the Nuke block has changed. This was required to give the ax argument a default.
Developer Changes
- New animation unittesting framework
- Tests / doc building now runs on CircleCI.

Fix packaging of the .animations and .blocks subpackages.

Animatplot now features a whole new API.

Built on the concept of blocks.

Now has documentation!