It looks like glm 0.9.6 supports matrix decomposition
http://glm.g-truc.net/0.9.6/api/a00204.html
#include <glm/gtx/matrix_decompose.hpp>
glm::mat4 transformation; // your transformation matrix.
glm::vec3 scale;
glm::quat rotation;
glm::vec3 translation;
glm::vec3 skew;
glm::vec4 perspective;
glm::decompose(transformation, scale, rotation, translation, skew, perspective);