Incremental housekeeping cleanup of test_misc.py

- standard/local import grouping
- docstring every test
- pep8 formatting
- remove custom assertion messages
- Separate tests to individual groups
- Remove unnecessary time.sleep() calls
- use echo=False parameter, avoiding testing
  combinations of mixed input+output, and removing
  the need to document this strange combination.
- programmatically test searcher_re/_string
- prefer assertRaises/assertRaisesRegexp
- use tempfile.gettempdir() instead of /tmp
Merge pull request #78 from pexpect/improve-upon-test-misc

Incremental housekeeping cleanup of test_misc.py