version 2.4

Maintenance release

2.4.1 Date 17 Jun 20177
- simplification of Clifford exponents
- trigsimp inncorporated in cliffsimpall
- sloving 

2.4 Date 27  Nov 2016
- new implementation clicoeff
- new implementation clidual
- convenience matrix functions
- added algebraical dual functionality
- fixed regressive product
- added Hestenes product
- added xor function