Imports of mapreplay command

PathSynopsis
contextPackage context defines the Context type, which carries deadlines, cancellation signals, and other request-scoped values across API boundaries and between processes.
flagPackage flag implements command-line flag parsing.
github.com/golang/glogPackage glog implements logging analogous to the Google-internal C++ INFO/ERROR/V setup.
github.com/google/trillianPackage trillian contains the generated protobuf code for the Trillian API.
github.com/google/trillian/testonly/internal/hammer
google.golang.org/grpcPackage grpc implements an RPC system called gRPC.
osPackage os provides a platform-independent interface to operating system functionality.
regexpPackage regexp implements regular expression search.
strconvPackage strconv implements conversions to and from string representations of basic data types.
stringsPackage strings implements simple functions to manipulate UTF-8 encoded strings.