add README for python-build.

was copied from [ruby-build](https://github.com/sstephenson/ruby-build).
import recent changes from ruby-build 20130408
update default pip version (1.2.1 -> 1.3.1)
update distribute version (0.6.34 -> 0.6.36)
revert distribute version (0.6.36 -> 0.6.32) due to the installation
problem with Jython 2.5.[01] (#15)
revert pip version (1.3.1 -> 1.2.1) to avoid AttributeError on Jython. (#15)

    AttributeError: 'module' object has no attribute 'O_NOFOLLOW'
Merge branch 'issue15'
fix typo to verify jar's checksum
add jython versions; jython-2.5.4-rc1 and jython-2.7-beta1
add pypy-2.0-beta2
fix completion problem on zsh
bundle patches into python-build repository
find appropriate patch for package automatically
remove useless patches
Merge branch 'automated-patching'
add workaround for incompatible behaviour of svnversion (#14)
fix build problem of ssl module with recent OpenSSL

http://bugs.python.org/issue12012
fix build problem of ssl modulle of CPython 3.0.1
remove needless declaration of LDFLAGS.

removing this not breaks build on latest Debian sid.
move patches into ./share to fix the install.sh