reading on uninitialized buffer can cause UB (`impl<R> BufRead for GreedyAccessReader<R>`)

Affected versions of this crate creates an uninitialized buffer and passes it to user-provided Read implementation.

This is unsound, because it allows safe Rust code to exhibit an undefined behavior (read from uninitialized memory).

The flaw was corrected in version 0.1.1 by zero-initializing a newly allocated buffer
before handing it to a user-provided Read implementation.