clarify rake version number in README
clarify rake version number in README

adammck/crabgrass,adammck/crabgrass,ajturner/crisiscommons,adammck/crabgrass,nilclass/echosocial,ajturner/crisiscommons,geoiq/digitalgazette,riseuplabs/crabgrass,adammck/crabgrass,riseuplabs/crabgrass,ajturner/crisiscommons,riseuplabs/crabgrass,geoiq/digitalgazette,geoiq/digitalgazette,riseuplabs/crabgrass,riseuplabs/crabgrass,riseuplabs/crabgrass,riseuplabs/crabgrass,ajturner/crisiscommons,nilclass/echosocial,nilclass/echosocial,nilclass/echosocial,geoiq/digitalgazette