Update import for INameChooser for Plone 4.3

Plone 4.3 removes many outdated packages and tidies up imports: http://plone.org/documentation/manual/upgrade-guide/version/upgrading-plone-4.2-to-4.3/updating-package-dependencies
This change will need to be revised if Plone 4.0 support is required for plone.api
Only test for the subset of views which exist for all versions of Plone

Removing cutObject and refreshPortlet since they don't exist for Plone 4.3
Fix: can't use set notation (like {'a', 'b'} in code that has to support python2.6.
Fix portal tests for Plone 4.3

Only test for common items in the registry and the available tools
Merge pull request #76 from cillianderoiste/p43tests

This fixes the tests for Plone 4.3 (Python 2.7)
Merge pull request #67 from thet/master

Changelog, RST and declaring dependencies
do not assume that plone.registry is installed. Fixes compatibility issue with plone 4.0/4.1
this should be a warning.
Indicate which functions are not available.
Merge branch 'master' of github.com:plone/plone.api
Update the URL to the exceptions documentation on RTD
use Asko's buildout cache trick to speed up Travis builds
indentation fixes
Merge pull request #77 from plone/issue72

Do not assume that plone.registry is installed
we now officially support Plone 4.3
Fix Sphinx warnings.

Most of them were due to invisible-code-blocks. As per
http://svn.zope.org/manuel/trunk/src/manuel/index.txt:

The "invisible-code-block" directive will work with either one or two
colons.  The reason is that reST processers (like docutils and Sphinx) will
generate an error for unrecognized directives (like invisible-code-block).
Therefore you can use a single colon and the line will be interpreted as a
comment instead.

For this reason we are now using a single colon after the
invisible-code-block directive.
GH-71 get the portal path with absolute_url_path so that it content.get works with sites which don't have the portal in the zope root

I don't know a nice way to write a test for this since the test layer assumes that the portal is in the site root. I have tested it manually with a local instance.
Remove unused variable
Merge pull request #78 from cillianderoiste/GH-71

#GH-71 fix content.get path to also work when the portal is not in the zope root
switch to flake8 that combines latest pep8 and latest pyflakes
Style guide for code blocks