Initial commit of expect 100-continue support
Also support HTTP with expect 100 continue

This creates an HTTP (not HTTPS) subclass and just
copies the class dictionary of the HTTP method overrides
into the HTTPS subclass.  Added an integration test for this
as well.
Fix failing tests
Fix py3 test failure
Reset response class when not handling expect 100 continue
Merge branch 'release-0.50.0' into develop

* release-0.50.0:
  Bumping version to 0.50.0
Use get_config_variable instead of profile attr

session.get_config_variable('profile') != session.profile.

In the case of "--profile", we set the session.profile attr,
but in the case of the env var, we look it up when we create
the scoped config or when we call get_config_variable('profile').

I think this can probably be fixed such that we always set
session.profile, but this fixes the immediate issue of
aws/aws-cli#805.
Fix ec2 ModifyVolumeAttribute model

`AutoEnableIO` is AttributeBooleanValue type, not Boolean type.

Fixes aws/aws-cli#803
Merge branch 'profile-env-var' into develop

* profile-env-var:
  Use get_config_variable instead of profile attr
Add endpoint heuristics module

This module will take input data (service_name, region_name, etc)
and construct a complete URL.
Move data loader over to component locator object
Integrate endpoint heuristics into botocore
Remove check for service name in s3

This can never happen because we subscribe to a specific
s3 event.  This was mentioned in code review feedback.
Remove _regions from botocore
Merge branch 'expect-100' into develop

* expect-100:
  Remove check for service name in s3
  Reset response class when not handling expect 100 continue
  Fix py3 test failure
  Fix failing tests
  Also support HTTP with expect 100 continue
  Initial commit of expect 100-continue support
Sync with the latest ec2 model
Merge branch 'quiver-fix-ec2-modify-volume-attribute-model' into develop

* quiver-fix-ec2-modify-volume-attribute-model:
  Sync with the latest ec2 model
  Fix ec2 ModifyVolumeAttribute model
Merge branch 'endpoint-rules' into develop

* endpoint-rules:
  Remove _regions from botocore
  Integrate endpoint heuristics into botocore
  Move data loader over to component locator object
  Add endpoint heuristics module
Fix failing test from endpoint heuristics

Use the endpoint resolver to find the region name override.
Otherwise it's possible that a ``None`` value can be passed
as a ``region_name`` value to handlers, which we don't want.
Revert "Merge branch 'expect-100' into develop"

The expect-100 changes do not work in python2.6.

The internal structure of HTTPConnection is different
in python2.6 so this needs to be reworked.

I'm still fairly confident that this can be done in python2.6,
it just needs additional research and time.

This reverts commit a23770e72758674a4274d68182f6a99d83810880, reversing
changes made to 13e8eecf9a1f887ca4e55de4d3c92aedb88deec5.