elixir version of nucleotide-count changed: one element lists like 'C' or 'T' replaced by characters like ?C or ?T.

'abc' is elixir is not a string, this is a list of integers.  This is not Ruby. This is the erlang VM.

```
iex(5)> [97, 98, 99]
'abc'
```

Thus, the first characters of `'AATAA'` is not `'A'`! The first character of `'AATAA'` is 65, or `?A`

The erlang and elixir way to denote characters is via this `?` notation.

Thus it makes absolutely no sense to use one element lists like 'A' or 'C' for this assignment when the erlang/elixir way is using characters like ?A and ?C.