pip install -e .[dev] Update README

[chasejohnson3]

I am new to contributing to pydra, and in the Developer installation instructions, pydra can be installed in developer mode using
pip install -e .[dev]
This syntax does not work in mac zsh, as identified here: pip install -e .[dev] error in mac zsh. They suggest pip install -e ".[dev]" works universally.

I suggest the following changes to the pydra README:
pip install -e .[dev] -> pip install -e ".[dev]"
pip install -e .[dask] -> pip install -e ".[dask]"

I would be happy to make this change as my first PR if these changes are desired.

[chasejohnson3]

If the above suggestions are accepted, I have implemented the changes above in PR #386.

[effigies]

#386 merged. Thanks!