partial_sort contains Out-of-bounds Read in release mode

Affected versions of this crate were using a debug assertion to validate the last parameter of partial_sort(). This would allow invalid inputs to cause an out-of-bounds read instead of immediately panicking, when compiled without debug assertions.

All writes are bounds-checked, so the out-of-bounds memory access is read-only. This also means that the first attempted out-of-bounds write will panic, limiting the possible reads.

The accessible region is further limited by an initial bounds-checked read at (last / 2) - 1, i.e., it is proportional to the size of the vector.

This bug has been fixed in v0.2.0.