Writes a specified number of LCM DoubleItems messages to a specified number 
of channels a specified number of times. See doubleItems.lcm for LCM 

To build:
g++ -o lcmpubtest -I . lcmPubTest.cc -llcm

usage: ./lcmpubtest nLoops sleepMsec, nChan, nItems
nLoops - loop this many times
sleepMsec - millisec to sleep between loops
nChan  - write to this many channels
nItems - write this many DoubleItem objects each time