Update memory.rmd

"cleaned" to "gleaned"
Fix two typos

Someimes -> Sometimes
get and get -> get and set
fix typo

yes and yes! are not exactly equivalent
distinguish between … and ….

`...` followed by a full stop looks like four dots. I've suggested inserting a space (in three places), but a better solution would be to reword avoiding ending the sentence with `...`.
Uneeded words?
Moved full stop.
Typo fix.
Added full stop.
Unneede bullet or missing exercise?
omit trailing comma
A fair number of typos fixed

nothing controversial (I hope!)
Typo.
Typo.
Word order, missing words.
Moved full stop.
Typo.
Typo.
Typo fix.
Typo?
Added full stop.