support strings that don't have matches

[KevinColemanInc]

If a string doesn't have a matching phrase, then it fails with an Enum.EmptyError

Sentient.analyze(" ")
Sentient.analyze("abcd")

[slashdotdash]

@KevinColemanInc This appears to be fixed by commit 4f862f7 but has not been published to hex.

A workaround is to reference that commit hash in mix.exs:

defp deps do
  [{:sentient, github: "dantame/sentient", ref: "4f862f7d1f5bdd1aab3d7fdb602f022a3c138d63"}]
end

@dantame Could you please bump the version and publish to hex.