beetbox.sh provide beet repo as argument for testing in forks

[AlexSkrypnyk]

BEET_REPO variable is currently hardcoded to main beetbox repo URL. When authoring roles there is a need to run role test on a fork of beetbox that has role's integration.

Proposed solution: Allow providing repo URL as first optional argument. If argument is not provided, the repo URL will default to main beetbox repo URL.

This will change circle.yml for roles from this

---
dependencies:
  override:
    - bash <(curl -fsSL http://bit.ly/beetbuild)
test:
  override:
    - sudo cp ~/$CIRCLE_PROJECT_REPONAME/tests/config.yml /beetbox/.beetbox/config.yml
    - bash <(curl -fsSL http://bit.ly/beetbuild)

to this

---
dependencies:
  override:
    - bash <(curl -fsSL http://bit.ly/beetbuild) https://github.com/user/beetbox
test:
  override:
    - sudo cp ~/$CIRCLE_PROJECT_REPONAME/tests/config.yml /beetbox/.beetbox/config.yml
    - bash <(curl -fsSL http://bit.ly/beetbuild) https://github.com/user/beetbox

[thom8]

@alexdesignworks this is already possible with an environment var on Circle CI.

machine:
  environment:
    BEET_REPO: https://github.com/user/beetbox

[thom8]

You can also set the branch to use with BEET_VERSION: new_feature