Simplify some regular expressions

* /\w/ including /\d/
* /\s/ including [/\r/, /\t/, /\n/]
Squash warning in defline.rb: assigned but unused variable - idtype
Squash warning in alignment.rb: assigned but unused variable - lines
Squash warning in alignment.rb: assigned but unused variable - oldkeys
.travis.yml: rbx-18mode is moved to allow_failures
Fix indent in test/unit/bio/appl/test_blast

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* warning: mismatched indentations at ...
Fix indent in test/unit/bio/db/genbank/test_genbank

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* warning: mismatched indentations at ...
Fix indent in test/unit/bio/db/test_phyloxml

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* warning: mismatched indentations at ...
Fix indent in test/unit/bio/sequence/test_dblink

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* warning: mismatched indentations at ...
Remove unused variable in test/unit/bio/db/embl/test_embl

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* warning: assigned but unused variable
Remove unused variable in test/unit/bio/db/embl/test_embl_rel89

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* warning: assigned but unused variable
Remove unused variable in test/unit/bio/db/embl/test_sptr.rb

 * Remove warnings "warning: assigned but unused variable"
 * Note that the sequence in TestSPTRUniProtRel7_6#test_10000aa is
   a fragment of human p53 protein, and is not related with Q09165.
Comment out some lines to suppress "unused variable" warnings
Remove unused variable in test/unit/bio/db/test_phyloxml_writer

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* warning: assigned but unused variable
Remove unused variable in test/unit/bio/io/flatfile/test_splitter

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* warning: assigned but unused variable
Add assertions and suppress "unused variable" warnings

 * Add assertions to check object id returned by forward_complement
   and reverse_complement methods. This change also aims to suppress
   "assigned but unused variable" warnings.
Remove unused variable in test/unit/bio/appl/bl2seq/test_report

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* warning: assigned but unused variable
Remove unused variable in test/unit/bio/appl/blast/test_report

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* warning: assigned but unused variable
Fix indent in lib/bio/map

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* warning: mismatched indentations at ...
Remove unused variable in lib/bio/appl/blast/report

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* warning: assigned but unused variable