Ploomber

- Removes `matplotlib` from dependencies, now using `IPython.display`
for inline plotting
- Fixes bug that caused custom args to
`{PythonCallable, NotebookRunner}.develop(args"--arg=value")` not
to be sent correctly to the subprocess
- `NotebookRunner` (initialized from ipynb) only considers the actual
code as its source, ignores the rest of the JSON contents
- Fixes bug when `EnvDict` was initialized from another `EnvDict`
- `PythonCallableSource` can be initialized with dotted paths
- `DAGSpec` loads `env.yaml` when initialized with a YAML spec and
there is a `env.yaml` file in the spec parent folder
- `DAGSpec` converts relative paths in sources to be so to the
project's root folder
- Adds `lazy_import` to `DAGspec`, to avoid importing `PythonCallable`
sources (passes the dotted paths as strings instead)

- `ploomber interact` allows to switch DAG parameters, just like
`ploomber build`
- Adds `PythonCallable.develop()` to develop Python functions
interactively
- `NotebookRunner.develop()` to develop now also works with Jupyter
lab

- Dropping support for Python 3.5
- Removes `DAGSpec.from_file`, loading from a file is now handled
directly by the `DAGSpec` constructor
- Performance improvements, DAG does not fetch metadata when it doesn't need to
- Factory functions: Bool parameters with default values are now
represented as flags when called from the CLI
- CLI arguments to replace values from `env.yaml` are now
built with double hyphens instead of double underscores
- `NotebookRunner` creates parent folders for output file if they don't exist
- Bug fixes

- NotebookRunner.develop accepts passing arguments to jupyter notebook
- Spec API now supports PythonCallable (by passing a dotted path)
- Upstream dependencies of PythonCallables can be inferred via the
`extract_upstream` option in the Spec API
- Faster `DAG.render(force=True)` (avoid checking metadata when
possible)
- Faster notebook rendering when using the extension thanks to the
improvement above
- `data_frame_validator` improvement: `validate_schema` can now
validate optional columns dtypes
- Bug fixes

- Improved `__repr__` methods in PythonCallableSource and
NotebookSource
- Improved output layout for tables
- Support for nbconvert>=6
- Docstrings are parsed from notebooks and displayed in DAG status table ([242](https://github.com/ploomber/ploomber/issues/242))
- Jupyter extension now works for DAGs defined via directories (via
`ENTRY_POINT` env variable)
- Adds Jupyter integration guide to documentation
- Several bug fixes

- Improved support for R notebooks (`.Rmd`)
- New section for `testing.sql` module in the documentation