Templates for practice exercises

[tasxatzial]

Since we already have written templates for a good number of exercises, in this issue, I'll attempt to collect all the parameters that currently influence how an exercise is written. This will serve as a reference for:

• How tests are generally written
• How to handle error cases and input validation
• How to write stubs
• How to address inconsistencies in terminology between the problem specifications and the Clojure implementation
• How to decide on the types of input and output

The older issues that currently discuss these topics are:

• How to handle input validation and other exceptions in exercises?
• Descriptions and tests may be misleading regarding the type of both input and expected values
• Template for tests
• [v3] Template for Exercises
• Add section to exercise READMEs for input/output format?

As part of the housecleaning, I'll be closing all these issues. We can reference them from this issue if we ever need them.

[tasxatzial]

Reserved for the template guidelines