Ploomber

- Deprecates `ploomber new` and `ploomber add`
- Adds `ploomber scaffold`
- Jupyter plugin now exports functions as notebooks using
`jupyter_functions_as_notebooks` in `pipeline.yaml`

- `ploomber add` generates template tasks and functions if they don't exist
- Jupyter plugin now shows PythonCallable tasks as notebooks

- Documentation tutorials re-organization and CSS fixes
- Improvements to the `InMemoryDAG` API
- Minor bug fixes
- `File.__repr__` shows a relative path whenever possible

- Adds support for passing glob-like patterns in `ploomber build` (via
`DAGSpec.from_directory`)

- Full Windows compatibility
- Adds documentation to show how to customize notebook output using
`nbconvert`
- Improvements to introductory tutorials
- Adds `--debug/-d` option to `ploomber build` to drop a debugger if
an exception happens
- Ensuring all dag-level, task-level and product-level clients are
closed after `dag.build()` is done
- Minor bug fixes

- 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)