Remove dependency on Pkg

[giordano]

I think there are two problems here:

• the main package requires Pkg:

  Herb.jl/Project.toml

  Line 13 in 13e8b88

  Pkg = "44cfe95a-1eb2-52ea-b672-e2afdf69b78f"

  while not using it anywhere in the source code. This should be solved by just removing that line in Project.toml
• the tests use Pkg to run the tests of upstream packages:

  Herb.jl/test/runtests.jl

  Lines 15 to 26 in 13e8b88

  	println("\n--- HerbConstraints tests ---")
  	Pkg.test("HerbConstraints")
  	println("\n--- HerbCore tests ---")
  	Pkg.test("HerbCore")
  	println("\n--- HerbInterpret tests ---")
  	Pkg.test("HerbInterpret")
  	println("\n--- HerbGrammar tests ---")
  	Pkg.test("HerbGrammar")
  	println("\n--- HerbSearch tests ---")
  	Pkg.test("HerbSearch")
  	println("\n--- HerbSpecification tests ---")
  	Pkg.test("HerbSpecification")

  This package looks like a metapackage which pulls together multiple packages, which is fine, but I'm not sure just running upstream packages test is a good approach, since they are already tested individually. Can there be integration tests, for example based on the tutorials in the docs, to make sure they keep working?

[ReubenJ]

Thanks for the suggestion, @giordano! Removing the dependency on Pkg definitely makes sense. I had started adding workflows for doctests to the individual repositories in #63, and I could also see doctests on the tutorials replacing the individual package tests in this meta package. If it's as easy as copying similar changes over from what I was working on in #63, I can get this updated soon. Otherwise, we'll put it on our to-do list to address soon.

Thanks again for the suggestion!