Fix ordering of assignments in FastQReader constructor.

[cmnbroad]

FastQReader doesn't handle leading blank lines correctly in all constructors.

• [x ] Code compiles correctly
• [x ] New tests covering changes and new functionality
• [x ] All tests passing
• Extended the README / documentation, if necessary
• Is not backward compatible (breaks binary or source compatibility)

[codecov-io]

Codecov Report

Merging #878 into master will increase coverage by 0.019%.
The diff coverage is 100%.

@@               Coverage Diff               @@
##              master      #878       +/-   ##
===============================================
+ Coverage     65.006%   65.025%   +0.019%     
- Complexity      7229      7235        +6     
===============================================
  Files            528       528               
  Lines          31894     31894               
  Branches        5444      5444               
===============================================
+ Hits           20733     20739        +6     
+ Misses          9013      9012        -1     
+ Partials        2148      2143        -5

Impacted Files	Coverage Δ	Complexity Δ
...c/main/java/htsjdk/samtools/fastq/FastqReader.java	82.432% <100%> (+1.351%)	26 <0> (+2)	⬆️
...sjdk/samtools/util/Md5CalculatingOutputStream.java	71.795% <0%> (-7.692%)	8% <0%> (-1%)
...main/java/htsjdk/samtools/SAMRecordSetBuilder.java	89.113% <0%> (+0.806%)	64% <0%> (+2%)	⬆️
src/main/java/htsjdk/samtools/util/StringUtil.java	67.692% <0%> (+1.538%)	67% <0%> (+2%)	⬆️
...samtools/util/AsyncBlockCompressedInputStream.java	76% <0%> (+4%)	13% <0%> (+1%)	⬆️

[lbergelson]

@cmnbroad 👍