Add ability to specify basic auth creds via environment variable

Useful for testing and running against a local GraceDB instance.
11 jobs for http in 8 minutes and 37 seconds (queued for 4 minutes and 33 seconds)
latest
Status Job ID Name Coverage
  Build
passed #534408
build:debian:jessie

00:03:40

passed #534409
build:debian:stretch

00:01:47

passed #534407
build:el7

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passed #534406
build:tarball

00:00:25

 
  Test
passed #534415
docs

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passed #534416
syntax

00:00:48

passed #534410
test:python2.7

00:00:47

passed #534411
test:python3.4

00:00:56

passed #534412
test:python3.5

00:00:47

passed #534413
test:python3.6

00:00:50

passed #534414
test:python3.7

00:00:50