Grouped Seq-specific methods.
Added pending tests.
Code formatting.
Rearranged test.
Added test for Traversable.aggregate.
Added test for Traversable.collectFirst.
Added test for Traversable.reduce.
Improved test cases.
Added test for Traversable.scan
Added test for Traversable.scanLeft
Added test for Traversable.scanRight
Added test for Traversable.contains
Added test for Traversable.containsSlice
Added test for Seq.endsWith
Added test for Seq.indexOf
Added test for Seq.segmentLength
Added test for Seq.prefixLength
Added test for Seq.indexOfSlice