Tweak language to make it clear that we're talking about building
testtools for the purpose of hacking on it, rather than installing it
for production or end use.

Warn against interactions with easy_install.

Fix the call to the parent setup.

This can be used e.g. 'pip install -e .[test]'

Change-Id: I51c0411af37ab2c43d068d22f0e3473dd958c7ba

In the documentation example, the name of the class is wrong in the super call.

This automates the manual dance around version numbers for less maintenance pain.

The main visible changes are:
- requirements are in requirements.txt for now
- tags must be just x.y.z not testtools-x.y.z
- version information in __init__ is dynamically looked up.
- we can probably cleanup a bunch of our bootstrap import glue but in
  the interest of clear reviews, and avoiding surprises, I'm leaving
  that alone for now.

Change-Id: Ia54f681b50764a94ada68a6b2ac1bc77bfb619c5

unittest2 recently added the ability to show local variables in
tracebacks as https://github.com/testing-cabal/testtools/issues/111
requested for us. Reusing that requires some refactoring of our code,
in particular where we were reimplementing bits of the traceback
module. Now we can just hard-depend on traceback2 and linecache2 which
are brought in by unittest2 1.0.0.

Change-Id: Ieb3268029d26b48ed4fcd25ed644bd339f6aa3fb

Fix a long-standing bug where tearDown and cleanUps would not be
called if the test run was interrupted. This should fix leaking
external resources from interrupted tests.
(Robert Collins, #1364188)

Fix a long-standing bug where calling sys.exit(0) from within a test
would cause the test suite to exit with 0, without reporting a failure
of that test. We still allow the test suite to be exited (since
catching higher order exceptions requires exceptional circumstances)
but we now call a last-resort handler on the TestCase, resulting in an
error being reported for the test.
(Robert Collins, #1364188)

Change-Id: I0700f33fe7ed01416b37c21eb3f3fd0a7ea917eb

Because post 1.0.0 software needs that.

Change-Id: I1802f0947f8b1027b71c75c41fb7c16aafb276ba

Change-Id: I3aa9150d0db5952053060f84d431b5b7fdea747e