Remove the logic (but keep the code, for now) which removes chilled assumptions from the list of assumptions; it doesn't seem to be needed, and sometimes throws away useful information. Probably, removing this information was the wrong thing to do in the first place, and that that 'fix' was actually just patching a bug elsewhere, which has now been actually fixed (but not by this change).
Remove the logic (but keep the code, for now) which removes chilled assumptions
from the list of assumptions; it doesn't seem to be needed, and sometimes throws
away useful information. Probably, removing this information was the wrong thing
to do in the first place, and that that 'fix' was actually just patching a bug
elsewhere, which has now been actually fixed (but not by this change).

This closes #57.

zaxtax/hakaru,zaxtax/hakaru,zachsully/hakaru,zachsully/hakaru