Fix to handle newlines appropriately.

[mcaidans]

When sending SMS, newlines will be counted as 2 chars. Currently the code does not handle this (besides \r\n).
Find below my fix for this to rectify this issue.
main.py 18-21

NL_CHARS = {
        '\n': 10,
        '\r': 13
    }

main.py 76-88

nl_count = 0
for index, c in enumerate(textlist):
    if c == cls.NL_CHARS['\n']:
        if index >= 1 and textlist[index - 1] == cls.NL_CHARS['\r']:
                # If part of \r\n keep count same (remove 1 as chars counted as 2 in first place)
                nl_count -= 1
                continue

        nl_count += 1
    elif c == cls.NL_CHARS['\r']:
        nl_count += 1

length += nl_count