Add importnb

[nrbgt]

• fixes use importnb for (functional) examples #28
• add importnb, resolve envs
• rework robot to require less copy/pasta
• update examples to use importnb functional style
  • 00_Introduction.ipynb
  • 01_Linking.ipynb
  • 02_Transformer.ipynb
  • 03_App.ipynb
  • 04_Interactive.ipynb
  • 100_node_label_placement.ipynb
  • 101_text_sizer.ipynb
  • 102_layout_options.ipynb
  • 103_transformer_layout_options.ipynb

[nrbgt]

While this isn't fully done, getting it merged early-ish would help with e.g. confidently merging #24 into #27... if it's green, it's probably good to go.

[nrbgt]

Should be smoother sailing now that i just copy the whole examples into the test directory.

[nrbgt]

Looks like I really made windows angry somehow, but otherwise this is almost ready for review/merging for real.