Add more tests with unittest.
Better tests. Add note for bugs.
Don't supress output to stderr.
Skip tests to send email.

Travis CI cannot send email.
Split tests for Travis and local run.
Rename test to tests.

This is to avoid name collision. Travis will think test pacakage as the
homonyous standard library.
Add explanations for coverage.
Merge pull request #4 from fossilet/syshook

Override system exception hooks