Docs, fix grammar

Remove TABs from debug-deadlock.py, so it works on py3

Raise FileNotFoundError if the core file is unreadable/non-existent

Document useful invocation

In some dumps, __pthread_mutex_lock is not in frame 2

Python2.6 compatibility.

Fix example so it handles mutex-owner that does not exist anymore.

Some dumps display "LWP 123" instead of "Thread 0x432 (LWP 123)".

Improve relevant thread search heuristic.

Minor tweaks.

Python3 compatibility.

Move debug-deadlock out of the main source and into examples.

Add pycoredump, add README, add deadlock debugging example.

Initial commit