Allow registering the dict->IContext adapters other than at import time.
Fix PIL dependency for Travis CI.
Trying to fix another pip dependency.
Allow registering the IContext->IXXXContext adapters other than at import time.
Merge branch 'master' into fix/global-adapters-registration

# Via Ioannis Tziakos (1) and IoannisTziakos (1)
* master:
  use the right environment variable
  we need cython after all
  more updates
  add etsdevtools in the installation
  install unittest2 when running under python 2.6
  add blockcanvas in the setup
  add apptools in the trvis-ci configuration
  remove cython since it should not be required
  update travis configuration
  add a dev-requirements file
  add a coverage rc configuration

Conflicts:
	.travis.yml
Merge pull request #15 from enthought/fix/global-adapters-registration

Allow registering the dict->IContext adapters other than at import time.