By converting dependencies to _, the 1.10.2 release scrambled the requirements in the json file, moving all "dependencies" to "external dependencies" with an underscored pypi name instead of the library name (adafruit_circuitpython_hid instead of adafruit_hid).

This PR uses - not _ to reference modules from dependencies, so it matches the index used in package_list and the pypi_name field. Use the same function in both parts to emphasize their relatedness. The original name before transformation is still used in external_dependencies.

Note: this does not keep the same format as pipkin as intended by #90. pipkin can map the format function on the list to make sure every reference uses the same format without having to edit the list manually.

Additionally:

• Add ~[; to filter requirements and strip() spaces. See here examples of valid formats.
• Use sets to simplify the uniqueness test. Previously if line in dependencies would always be False. (testing the presence of adafruit-circuitpython-dotstar before adding adafruit_dotstar).
• Add spidev to the list of skipped dependencies. (Found in the community bundle).
• Sort the dependencies to make comparisons for that kind of check easier in the future. And use sort_keys in json, because why not.

With this PR the generated json matches the one generated by 1.10.1 except newly skipped libraries are skipped (pyasn1, pillow, spidev), and bad dependencies are fixed (typing-extensions~).