Fix wording for problem BASICS: get

Fixed issue https://github.com/nodeschool/discussions/issues/96 copied below:

Hi,

In the "Basics: GET" test, the requirements say:

"""The store will contain up to 10 entries with keys in the form:

gibberishX

Where 'X' is an integer between 0 and 100."""

When reading this, I thought that gibberishX is something like ohdfuhaosX and not the actual word 'gibberish'. I suggest to change 'gibberish' to 'level' (or 'key') and explain that that's the actual key prefix.