Stepwise

Feature
* Allow preset names to be reused ([`0ca56ed`](https://github.com/kalekundert/stepwise/commit/0ca56ed27568288f56fa7c04da7d4f578eaf20fe))

Feature
* Add the testing submodule ([`4e5a280`](https://github.com/kalekundert/stepwise/commit/4e5a280dbf4ff6f68512b3db4b2064a961d46b47))
* Add Quantity.from_string_or_float() ([`d44aa42`](https://github.com/kalekundert/stepwise/commit/d44aa4261ad7c0b973b32237459b81d7535de948))
* Let the user fully specify how reactions are introduced ([`f23624a`](https://github.com/kalekundert/stepwise/commit/f23624ad0ee1d8dbb8ef27e6e289cd6132a1c343))

Fix
* Don't share presets between instances ([`b074db7`](https://github.com/kalekundert/stepwise/commit/b074db73563ac0176f3536b2132f9cb20fe1b211))
* Don't show master mixes with only 1 reagent ([`acd5221`](https://github.com/kalekundert/stepwise/commit/acd52219f23ecd3c8c4c59b5e50ca4fd60c7b6ea))

Feature
* Allow negative reagent orders ([`dba0664`](https://github.com/kalekundert/stepwise/commit/dba066412cb472001075475ed997564c7d6fb12c))

Feature
* Add an Oxford comma function ([`1fc4b07`](https://github.com/kalekundert/stepwise/commit/1fc4b072cfd988afc7dee19031893271077356d3))

Feature
* Make Quantity a subclass of Real ([`3e91ecc`](https://github.com/kalekundert/stepwise/commit/3e91ecc9fe621d93f147b1ecc9e8d6b8b3d5383b))

Fix
* Report errors that occur when pickling protocols ([`df03481`](https://github.com/kalekundert/stepwise/commit/df034812e31d9b6798557c55cd1faca6567fb3e7))