bump merb-core version to 0.9.3 in prep for release.
bump merb-core version to 0.9.3 in prep for release.

merb/merb,wycats/merb,wycats/merb,wycats/merb,merb/merb,wycats/merb,wycats/merb,merb/merb,benburkert/merb-core,benburkert/merb-core