Update changelog for v0.5.1
Update changelog for v0.5.1

SymbiFlow/pycapnp,jparyani/pycapnp,tempbottle/pycapnp,rcrowder/pycapnp,rcrowder/pycapnp,jparyani/pycapnp,SymbiFlow/pycapnp,rcrowder/pycapnp,jparyani/pycapnp,jparyani/pycapnp,tempbottle/pycapnp,SymbiFlow/pycapnp,tempbottle/pycapnp,SymbiFlow/pycapnp,rcrowder/pycapnp,tempbottle/pycapnp