pread(0,0) raises EOFError #66

@casperisfine / @byroot thanks for the pread implementation!

However, there's a slight difference in how it treats the edge case of reading zero bytes from an empty file

File.open("empty_file").pread(0,0) # => ""
StringIO.new(File.read("empty_file")).pread(0,0) # => raises `end of file reached (EOFError)`

In our case, this is almost certainly a bug in the application logic where it ought to bail out early rather than trying to read zero bytes from the io, but thought it was worth highlighting the discrepancy.