Add actor example.
Change strand to use defer of underlying executor.
Use user-supplied allocator for scheduler, timer, strand and channel.
Use different small block recyclers for different purposes.
Use user-supplied allocator for the polymorphic executor's function objects.

If no allocator is specified, uses the small block allocator.
Merge remote-tracking branch 'upstream/master'
Squashed 'site_scons/' changes from 03c1d29..36f1395

36f1395 Update reference to License
17d5689 Add local install option to bootstrap example
d08c9e0 Add missing module reference
590f1ff Update version
e14a42a Add separate README.rst file for pypi
dc7ad5c Add build keyword
b82f978 Update log messages, version file location and classifiers for setup.py
cf5971e Update version and add license to manifest
322647e Fix test_runner/runner errors and add packaging files
9b25a24 Update README to show installation options and consolidate use of 'runner'
2fa0508 Fix reference to construct
1479ae6 Rename cppscons to cuppa
d4ad0d6 Rename sconstruct/construct to cppsons
e93fd59 Make construct into a package for easier install and fix boost toolset use

git-subtree-dir: site_scons
git-subtree-split: 36f13955a634a11bea558b96e03f27cc26dd42e5
Merge commit '89a9b4b081793ecf1b7d7a909a81e7b8ba0dcf24'