Roadmap to `v1`

[avhz]

This is the roadmap for getting RustQuant to a solid v1.

High priority to-do list:

• [ ] #303
• [ ] #245
• [ ] #88
• [ ] #141
• [x] #188
• [x] #5
• [x] #246
• [x] #247
• [ ] #14

Low priority to-do list:

• [x] #26 (prune dependencies where possible, for example)
• [ ] Implement a new MultiFactorStochasticProcess that can implement multi-factor models, such as Heston, SABR, Libor Market Model, Chen Model, etc.
• [ ] #143

Notes:

• Make use of #[derive(derive_builder::Builder)] where it makes sense, such as for building financial instruments. This also has the benefit of providing default arguments.