coverage-3.0b1

Major overhaul.

• Coverage.py is now a package rather than a module. Functionality has been split into classes.
• The trace function is implemented in C for speed. Coverage.py runs are now much faster. Thanks to David Christian for productive micro-sprints and other encouragement.
• Executable lines are identified by reading the line number tables in the compiled code, removing a great deal of complicated analysis code.
• Precisely which lines are considered executable has changed in some cases. Therefore, your coverage stats may also change slightly.
• The singleton coverage object is only created if the module-level functions are used. This maintains the old interface while allowing better programmatic use of coverage.py.
• The minimum supported Python version is 2.3.