Fails if key is an int

[jacobg]

A dictionary such as:

{1: "abc"}

will fail with this exception:

  File "/env/lib/python3.7/site-packages/animal_case/__init__.py", line 72, in parse_keys
    formatted[key] = parse_keys(value, types)
  File "/env/lib/python3.7/site-packages/animal_case/__init__.py", line 70, in parse_keys
    for key, value in _unpack(formatter(data)):
  File "/env/lib/python3.7/site-packages/animal_case/__init__.py", line 47, in keys_to_camel_case
    return {to_camel_case(key): value for key, value in _unpack(content)}
  File "/env/lib/python3.7/site-packages/animal_case/__init__.py", line 47, in <dictcomp>
    return {to_camel_case(key): value for key, value in _unpack(content)}
  File "/env/lib/python3.7/site-packages/animal_case/__init__.py", line 37, in to_camel_case
    content = value.split('_')
AttributeError: 'int' object has no attribute 'split'

It looks like the the to_camel_case function should return identity value if input value is not a string.

[rafa-acioly]

can you send a PR @jacobg ?