pack should use the --no-color equivelant when its not attached to a terminal

[zmackie]

Summary

---

#477 turned up the fact that color escape codes are leaking into output when pack is not attached to a terminal. It would be UX nicety for pack to run as the equivelant to --no-color when, eg. piping to less.

note the output below is with pack built from #478 (therefore has the docker progress bar stripped)

Reproduction

Steps

± zm |fix-477 ✓| → ./out/pack build gcr.io/cncf-buildpacks-ci/pm/issues/pack:478-asdas --publish -p ../samples/apps/java-maven/ | morebionic: Pulling from cloudfoundry/cnb
dbe632be70ad: ESC[90mPulling fs layerESC[0m
750afeac99ff: ESC[90mPulling fs layerESC[0m
59bb86436456: ESC[90mPulling fs layerESC[0m
71cd62cf076a: ESC[90mPulling fs layerESC[0m

Expected

Cleaner output:

± zm |fix-477 ✓| → ./out/pack --no-color build gcr.io/cncf-buildpacks-ci/pm/issues/pack:478-asdas --publish -p ../samples/apps/java-maven/ | more
bionic: Pulling from cloudfoundry/cnb
dbe632be70ad: Pulling fs layer
750afeac99ff: Pulling fs layer
59bb86436456: Pulling fs layer
71cd62cf076a: Pulling fs layer
1473b2bc3374: Pulling fs layer
5d932446918a: Pulling fs layer
34e057da544e: Pulling fs layer
81d29541bb33: Pulling fs layer
ea92060a149b: Pulling fs layer
c995ce118c19: Pulling fs layer
17c50dd57945: Pulling fs layer
1de1a037cfdb: Pulling fs layer
68d2c99148bc: Pulling fs layer
e0bce984d18b: Pulling fs layer
c09e86e44715: Pulling fs layer
696fd8bb65f4: Pulling fs layer

---

Environment

pack info

± zm |fix-477 ✓| → ./out/pack report
Pack:
  Version:  dev-2020-01-31-11:18:55
  OS/Arch:  darwin/amd64

Default Lifecycle Version:  0.6.0

Config:
  default-builder-image = "cloudfoundry/cnb:bionic"

docker info

[jromero]

Determining whether we are attached to the terminal seems to be pretty straight forward with use of terminal#IsTerminal().