Implemented method chaining for the Stream class.

Also added a test.
Added method chaining and test to Trace class.
Stream.verify() now able to method chain.
Adjusting doctests to method chaining.
Adjusting some remaining doctests.
Updated changelog
Using the processing chain for testing.
More informative docstrings.
PEP8 in doctests
Merge pull request #621 from krischer/method_chaining

Method chaining for Stream and Trace objects.