become an externally usable package but still remains within the main sqlalchemy parent package.
in this system, we use kind of an ugly hack to get the noseplugin imported outside of the
"sqlalchemy" package, while still making it available within sqlalchemy for usage by
third party libraries.

  - bootstrap and lib move to all absolute imports
  - testing.py is no longer internally referenced.
  - requirements move to be a pluggable class which can
    be overridden.
  - cleanup

in the interests of third party testing, test/lib and test/bootstrap
may move to be an independent package.

- rework bindtemplate system of "numbered" params by applying
the numbers last, as we now need to generate these out of order
in some cases
- add positional assertion to assert_compile
- add new cte_positional collection to track bindparams generated
within cte visits; splice this onto the beginning of self.positiontup
at cte render time, [ticket:2521]

- add a test suite for all the Engine/Connection/TLEngine transaction/begin
helpers/context managers
- update docs

issue I'm not exactly sure of what nature it is

CompileException for all type/statement compilation
issues, instead of InvalidRequestError or ArgumentError.
The DDL for CREATE TABLE will re-raise
CompileExceptions to include table/column information
for the problematic column.  [ticket:2361]

established after a failed flush would be committed
as part of the subsequent transaction that
begins automatically after manual call
to rollback().   The state of the session is
checked within rollback(), and if new state
is present, a warning is emitted and
restore_snapshot() is called a second time,
discarding those changes. [ticket:2389]

- repaired testing.assert_warnings to also verify
that any warnings were emitted