use gpickle r/w in linker

[cmcarthur]

(dbt-development-3.6) ✘-1 XXX [master|…1]
20:45 $ echo 'YAML TEST' && time python -m cProfile -o compile_profile.out ~/git/dbt/scripts/dbt compile --profile redshift
YAML TEST
^@Compiled 259 models, 101 tests, 0 archives, 0 analyses

real    0m20.827s
user    0m20.099s
sys     0m0.360s
(dbt-development-3.6) ✔ XXX [master|…1]
20:46 $ echo 'GPICKLE TEST' && time python -m cProfile -o compile_profile_gpickle.out ~/git/dbt/scripts/dbt compile --profile redshift
GPICKLE TEST
Compiled 259 models, 101 tests, 0 archives, 0 analyses

real    0m13.523s
user    0m12.786s
sys     0m0.293s

Wall time shows a 7sec speedup.

Snakeviz (YAML):

Couldn't visualize it with gpickle, but it took 5.166ms to write the graph file vs 7.58s for YAML.

[drewbanin]

@cmcarthur absolutely incredible