fix out of order output in process_paired_reads

[slambert-git]

Intermittent failures in test cases 06 and 09 of test_reads_when_count_false were caused by paired-end, interleaved records written out of order.

Maintain the order of records by calling .collect() on the ParIter before writing. Tests pass consistently now.

Disclaimer: I am very new to Rust. I apologize if this is unhelpful.

[slambert-git]

Also to note. I think tests would have failed more reliably if the test cases used more than 2 read pairs (have a 50/50 shot of getting the right order). Id be happy to add to the test data to this PR if it's appreciated.

[nh13]

@SheaML thank-you for spotting this, yes another PR would be great to add more read pairs. I am running lints the test suite (please make sure it passes, then I'll review). This is very much appreciated!

[nh13]

This LGTM, and mirrors the .flatten().collect() we're using for single-end/fragment reads. Very nice catch indeed!