extending capsule-capsule distance computation

  adding a test.

Add an accessor to shared pointer to CollisionGeometry member.

  - classes CollisionObject and ContinuousCollisionObject,
  - declare former accessors as deprecated.

fix boost/cstdint.hpp datatypes

Quoting the boost documentation:

<boost/cstdint.hpp> - Provides typedef's based on the
1999 C Standard header <stdint.h>, wrapped in namespace boost.

This invalid usage seems to break with glibc 2.18.

change the readme in markdown format

Fix bug: sphereSphereIntersect calculates wrong contact point

Fix compiler/linker errors in Visual Studio introduced by recent commits 

M_PI is not part of the C++ standard and thus Visual Studio does not define it by default.