Wrong value for camelize and decamelize when using 1 or 2 characters key

[ThmX]

Describe the bug
When using a key with only 2 characters, the value is not camelized nor decamelized correctly.

To Reproduce

assert humps.camelize("j1") == "J1"
assert humps.decamelize("J1") == "j1"

assert humps.camelize("x") == "X"
assert humps.decamelize("X") == "x"

Expected behavior

• camelize should return J1 but got j1 instead.

• decamelize should return j1 but got J1 instead.

• camelize should return X but got x instead.

• decamelize should return x but got X instead.

Desktop (please complete the following information):

• OS: Macos
• Browser None
• Version 3.8.0

Additional context
#61 and #168