added documentation
added documentation

updated the constructor documentation and added description for
the callback function.

mgogoulos/libcloud,Kami/libcloud,ByteInternet/libcloud,mgogoulos/libcloud,DimensionDataCBUSydney/libcloud,techhat/libcloud,SecurityCompass/libcloud,samuelchong/libcloud,Scalr/libcloud,StackPointCloud/libcloud,vongazman/libcloud,andrewsomething/libcloud,samuelchong/libcloud,iPlantCollaborativeOpenSource/libcloud,erjohnso/libcloud,lochiiconnectivity/libcloud,DimensionDataCBUSydney/libcloud,iPlantCollaborativeOpenSource/libcloud,NexusIS/libcloud,pquentin/libcloud,illfelder/libcloud,apache/libcloud,erjohnso/libcloud,pquentin/libcloud,apache/libcloud,wuyuewen/libcloud,mistio/libcloud,NexusIS/libcloud,erjohnso/libcloud,vongazman/libcloud,mistio/libcloud,lochiiconnectivity/libcloud,ByteInternet/libcloud,t-tran/libcloud,iPlantCollaborativeOpenSource/libcloud,Scalr/libcloud,StackPointCloud/libcloud,ZuluPro/libcloud,ZuluPro/libcloud,ZuluPro/libcloud,techhat/libcloud,mgogoulos/libcloud,andrewsomething/libcloud,t-tran/libcloud,samuelchong/libcloud,mistio/libcloud,SecurityCompass/libcloud,ByteInternet/libcloud,apache/libcloud,illfelder/libcloud,vongazman/libcloud,SecurityCompass/libcloud,t-tran/libcloud,andrewsomething/libcloud,StackPointCloud/libcloud,watermelo/libcloud,wuyuewen/libcloud,illfelder/libcloud,Kami/libcloud,lochiiconnectivity/libcloud,watermelo/libcloud,Scalr/libcloud,techhat/libcloud,Kami/libcloud,wuyuewen/libcloud,pquentin/libcloud,watermelo/libcloud,NexusIS/libcloud,DimensionDataCBUSydney/libcloud