Add javadoc and test for Sequence#flatten.
Add javadoc for Sequence#generate.
Add javadoc for Sequence#unfold.
Set timeout on each test of parallel operators.
Add javadoc for Sequence#alwaysThrow.
Simplify condition.
Correct minor issue.
Add javadoc for Sequence#characters.
Add javadoc for Sequence#range.
Add javadoc and test for Sequence#lines.
Correct minor issue in result type.
Separate tests.
Add javadoc and test for Sequence#words.
Add javadoc and test for Sequence#matches.
Add javadoc and test for OnFile utility.
Add javadoc and test for Sequence#repeat.
Optimize Sequence#generate.
Optimize Seq#disjoint.
Correct javadoc of Sequence#range.
Use pre-populated function for Sequence#words to reduce instance.