newtonian: update Newtonian noise calculation

Implements the changes recommended by Jan Harms in https://git.ligo.org/rana-adhikari/CryogenicLIGO/issues/45
Fixes #18
2 jobs for master in 9 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
failed #106873
test

00:00:09

 
  Deploy
skipped #106874
pages
 
Name Stage Failure
failed
test Test
Checking out c9652935 as master...
Downloading gwinc/test/A+.pkl (897 KB)
Error downloading object: gwinc/test/A+.pkl (6ec7119): Smudge error: Error downloading gwinc/test/A+.pkl (6ec7119694e3a92be24a62b572e494b12ea8c4f14a21279c6dec95b9adf4cb87): batch response: Access forbidden. Check your access level.

Errors logged to /builds/gwinc/pygwinc/.git/lfs/objects/logs/20180626T160157.031824887.log
Use `git lfs logs last` to view the log.
error: external filter 'git-lfs filter-process' failed
fatal: gwinc/test/A+.pkl: smudge filter lfs failed
ERROR: Job failed: exit code 1