Imports of sendspan command

PathSynopsis
flagPackage flag implements command-line flag parsing.
fmtPackage fmt implements formatted I/O with functions analogous to C's printf and scanf.
github.com/lightstep/lightstep-tracer-goPackage lightstep implements the LightStep OpenTracing client for Go.
logPackage log implements a simple logging package.
timePackage time provides functionality for measuring and displaying time.