QM 3.1.3 released

The QM 3.1.3 release (see https://sourceforge.net/projects/qpc/files/QM ) fixes the following bugs, all related to the history
connector (see https://sourceforge.net/p/qpc/bugs):

#95 "Resizing of state with history generates "Assertion failed" error."
#96 "Incoming transitions to a history connector stretch incorrectly
     when the state is moved"
#97 "Newly added history connector not moving when the state is resized."

NOTE: This release does not change the QM code generation in any way.