Tap tests: sort tap names for comparison

[mistydemeo]

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---

Since the directories returned by filesystem operations aren't necessarily in alphabetical order, this could fail in really pedantic ways:

 10) Failure:
TapTest#test_names [/home/vagrant/.linuxbrew/Library/Homebrew/test/test_tap.rb:108]:
--- expected
+++ actual
@@ -1 +1 @@
-["homebrew/core", "homebrew/foo"]
+["homebrew/foo", "homebrew/core"]

[MikeMcQuaid]

Makes sense, thanks @mistydemeo!