Tools to add/remove from book

[rowanhemsi]

Consider adding poetry and removing Travis from Tools page.
Consider adding a note to say that Rgovcookiecutter is still quite early in development

[rowanhemsi]

Second sentence here raises a more general point - do we want to include packages that are still early in development? The benefit would be to reduce the chance of duplication, but we may want to be careful about seeming to recommend packages that may not yet work.
A compromise may be including WIP packages under a subheading or adding a "work in progress" note

[Jacobb164]

Do we want to separate out early development tools and recommended? Under the early development tools we can cavate that they are useful but likely to change frequently.