Adjusting formatting in split_libraries_fastq

Line lengths adjusted, indentation adjusted, use of "is" and "is not" when
doing comparisons with None. Changed a try-except to use dict.get function.

Fixes #1251
Merge branch 'master' of https://github.com/qiime/qiime into issue1251
Add a new line

Fixes #1251
Fixing typo "opption_parser"
Merge pull request #1253 from adamrp/issue1251

Adjusting formatting in split_libraries_fastq