Release 0.5.1

Hello all,I'm pleased to announce 0.5.1 release.

This is a minor bugfix release; it is a recommended upgrade for users of 0.5.0.This release includes the following changes:

• builds with GCC 4.3
• re-enables regex support, which was inadvertently disabled in 0.5.0
• add better error handling to shapeindex
• support ppc64 builds
• fix division by zero error in placement_finder.cpp with multiple loops

Big thanks to Dominic Hargreaves for making it happen!