Try using gemsstash on PATH in test

Author: olleolleolle

spec/gemstash/cli_spec.rb

@@ -4,7 +4,7 @@
 
 RSpec.describe "CLI executable", type: :aruba do
   before do
-    run_command("exe/gemstash --version")
+    run_command("gemstash --version")
   end
 
   it { expect(last_command_started).to have_output(/Gemstash version \d\.\d\.\d/) }