added coalesced addition benchmark. (copy of normal one for now).
compile and benchmark with the following from within the src/ folder

clear; nvcc -arch=sm_30 benchmarks.cu normal_addition_benchmark.cu interleaved_addition_benchmark.cu coalesced_addition_benchmark.cu bignum_conversions.cpp random_bignum_generator.cpp -o ../bin/benchmarks -lgmp; nvprof --print-gpu-trace --normalized-time-unit us ../bin/benchmarks