force exact match on .get()

## Issue Description

when executing the following statement:

```
import arrow
arrow.get('95-03-10 23:01:44','YY-M-D HH:mm:ss')

```

the library returns me the date, but I gave it a single M, so it shouldn't have done the .get() but it did. one would expect it to fail, as the correct format should be 'YY-MM-D HH:mm:ss' for that same example.

I would like to know if this is a bug or is there a parameter to force the match to be exact?

## System Info

- 🖥 ubuntu 18.04 32 bits
- 🐍 Python 3.8.5
- 🏹 1.2.1

Start at the arrow.get() entry point using the reported format and input, and trace how format tokens are matched. Check the existing parsing behavior and any related tests; done means the expected handling of a single M versus MM is defined and covered consistently.

Written by the indexing model from the issue text.