Not shadowing the double function in core.
Merge branch 'solution'

Conflicts:
	test/clojure_workshop/ex_1.clj
_ should actually not be filled out in this case. Room for confusion.
Typos
Using different strings, makes it easier to find what is incorrect when reading test output.
Merge branch 'solution'

Conflicts:
	test/clojure_workshop/ex_2.clj