Don't write inside of the package directory

[maleadt]

During testing of this package, output is being written to a directory inside of the package:

Term.jl/test/10_test_inspect.jl

Lines 16 to 21 in 094339b

	# save expressions to file (for later comparisons)
	for (i, e) in enumerate(expressions)
	tofile(string(Dendogram(e)), "./txtfiles/dendo_expr_$i.txt")
	tofile(string(Tree(e)), "./txtfiles/tree_expr_$i.txt")
	tofile(sprint(expressiontree, e), "./txtfiles/exptree_expr_$i.txt")
	end

This is not OK, as packages can be installed in a read-only environment. As a result, this package fails testing on PkgEval.
For the time being, I'll blacklist testing of this package, but if this gets fixed feel free to ping me or open a PR on PkgEval.jl to resume testing.

[FedeClaudi]

Thanks