PIL removal

remove obsolete PIL/Imaging/Python Image Library,
it was used for image recognition, is now unsupported
and obsolete.

Used eg in people-tracking-demo
PIL add notice to demo using PIL

maybe it got broken, well, it's broken anyway
remove libpng

was used as dependency of PIL (obsoleted too)
mention PIL in requirements.txt for pip

Conflicts:
	external/common/requirements.txt
swarming logic is now a port of the nupic repo. Still need to migrate unit tests over
swarming logic is now a port of the nupic repo. Still need to migrate unit tests over
Dumps stdout from build.sh to a temp file.
Consolidate local variables before functions in build.sh.
Indentation/style fix to build.sh.
Indentation/style fix to cleanbuild.sh.
Make sure stdout file's directory exists.
Maybe I encrypted the AWS keys with the wrong repo slug. Trying again.
Merge pull request #196 from rhyolight/publish-artifacts

Maybe I encrypted the AWS keys with the wrong repo slug. Trying again.
Changing the file name of the archive file...

... to `nupic-${TRAVIS_JOB_NUMBER}.tar.gz` instead of `nupic-${TRAVIS_BUILD_NUMBER}.tar.gz`. This will enable archives for each part of the build matrix (python 2.6 and python 2.7).
Removing duplicate context in S3 path

https://s3-us-west-2.amazonaws.com/artifacts.numenta.org/artifacts/numenta/nupic/ --> https://s3-us-west-2.amazonaws.com/artifacts.numenta.org/numenta/nupic/
Missed a file name change, changed the name of the tar file.

From nupic-XXX.X.tar.gz to build-XXX.X.tar.gz because it's already going into a directory called 'nupic'.
Merge branch 'master' into verbosity
Merge pull request #190 from scottpurdy/verbosity

Verbosity fixes for build
WIP on a unit test for swarming
Revert to using --target option for pip to explicitly install to lib, as
opposed to specifying --prefix, which may result in it being installed in
lib64, which is causing problems in some environments.