Also, add code to automate such stripping in the future.  The diff
from commit addac276 to here is exactly the result of running that
code on the speeches added in commit addac276.

HTML still needs to be stripped, though.

The speech's text was duplicated, with a few very minor typographical
differences.  I went with the second copy.  This problem exists in the
source at the Miller Center site, so we should report it to them, but
in any case we might as well solve it here right away.

Thanks to Jason Levy for reporting the bug to me.

Also, remove the note in README.md about alternative sourcing for his
2019-09-25 speech before a press conference.  That speech's transcript
is now available from the Miller Center, who presumably got it from
the same White House web site page I got it from because it was
byte-for-byte the same.