Do not flush buffer every newline

[sstadick]

Adding STDOUT.flush_on_newline = false to the crystal bedcov implementation otherwise it flushes every line. On my laptop this gives bedcov nearly a 3.5 second speedup.

Relevant issue / forum posts from Crystal:

• Should STDOUT always set flush_on_newline by default? crystal-lang/crystal#7431
• https://forum.crystal-lang.org/t/crystal-0-34-0-slower/2124/43

[lh3]

Thanks!

[lh3]

Tables in README have been updated. Your change is indeed faster. Sort of surprising given that stdout is not frequently flushed in C. Stderr is flushed frequently.

[sstadick]

Well, I think this change puts it more in line with C. It was flushing every newline, now it flushes less frequently.