Update changelog for 0.5 release.
Update changelog for 0.5 release.

Clean up entries, add date.

tcmitchell/geni-ar,tcmitchell/geni-ar,tcmitchell/geni-ar,GENI-NSF/geni-ar,tcmitchell/geni-ar,charliemeyer/geni-ar,charliemeyer/geni-ar,GENI-NSF/geni-ar,GENI-NSF/geni-ar,tcmitchell/geni-ar,GENI-NSF/geni-ar,GENI-NSF/geni-ar,charliemeyer/geni-ar,charliemeyer/geni-ar,charliemeyer/geni-ar