test numeric value as input for issue #99

Try to add a test to demonstrate and possibly fix issue #99. The test fails but I don't understand why...

```
$ rspec
.....................F[deprecated] I18n.enforce_available_locales will default to true in the future. If you really want to skip validation of your locale you can set I18n.enforce_available_locales = false to avoid this message.
Translated 5 keys
+--------+----------------------+-------------------------------+
| Locale | Key                  | Value                         |
+--------+----------------------+-------------------------------+
|   es   | common.array_key     | ["Hola.", nil, "", "Adiós."]  |
|   es   | common.hello         | Hola - %{user} O'neill!       |
|   es   | common.hello_html    | Hola - <b>%{user} O'neill</b> |
|   es   | common.nil-value-key |                               |
|   es   | common.numeric-key   | 1                             |
+--------+----------------------+-------------------------------+
.................................................................................

Failures:

  1) Google Translation real world test #google_translate_list works with ["numeric-key", "nil-value-key", "key", "html-key.html", "array-key"]
     Failure/Error: expect(translations).to eq(tests.map { |t| [t[0], t[2]] })
       
       expected: [["numeric-key", 1], ["nil-value-key", nil], ["key", "Hola - %{user} O'neill!"], ["html-key.html", "Hola - <b>%{user} O'neill</b>"], ["array-key", ["Hola.", nil, "", "Adiós."]]]
            got: [["numeric-key", 1], ["nil-value-key", nil], ["key", "1"], ["html-key.html", "Hola - <b>%{user} O'neill</b>"], ["array-key", ["Hola - zxzxzx O'neill!", nil, "Hola.", ""]]]
       
       (compared using ==)
     # ./spec/google_translate_spec.rb:25:in `block (4 levels) in <top (required)>'

Finished in 6.12 seconds (files took 0.34055 seconds to load)
103 examples, 1 failure

Failed examples:

rspec ./spec/google_translate_spec.rb:21 # Google Translation real world test #google_translate_list works with ["numeric-key", "nil-value-key", "key", "html-key.html", "array-key"]
```