Automate code formatting and QA

[davnn]

Currently, code formatting is done manually using DocumentFormat.jl, which is error-prone and not restrictive enough. However, it appears that there is no clear solution to code formatting with Julia and this issue should bundle ideas for improvement.

Initial goals that come to my mind are:

• Formatting should be configurable, restrictive and preferably automatic
• Formatting checks should be performed locally and on CI
• Automatically check code formatting and run all tests before every commit

[davnn]

An example can be seen at: https://github.com/invenia/Models.jl/pull/31/files

[davnn]

Evaluate https://github.com/JuliaTesting/Aqua.jl for quality assurance.