Explain support for minor releases

[Julian-O]

I understand from the documentation that Homebrew can allow me to install, say, Python 2.6, Python 2.7 and Python 3.2.

However, it isn't clear whether it can install Python 2.7.2+, 2.7.4 and 2.7.5a1 at the same time. These generally have the same install directory (python27), so there is a difference, and this might not be supported.

The documentation should be changed to explicit state whether this is supported.