Add Travis build

[ronaldtse]

(Edited by @skalee)

• Test that formula passes brew audit. (extracted to Run "brew audit" in Travis CI #8)
• Test that stable version is installable from source.
• Test that HEAD version is installable from source.

[skalee]

I don't have write permissions to this repository, but following should work:

lang: minimal
os: osx

# Refer to: https://docs.travis-ci.com/user/reference/osx/#macos-version
osx_image:
  - xcode10.2
  - xcode9.4
  - xcode8.3
  - xcode7.3

env:
  global:
    TAP_NAME=riboseinc/rnp
    FORMULA_NAME=${TAP_NAME}/rnp
    OPTS=""

install:
  - brew update
  - brew tap ${TAP_NAME} "${TRAVIS_BUILD_DIR}"
  - brew install ${FORMULA_NAME} ${OPTS}

script:
  - brew test ${FORMULA_NAME}

matrix:
  include:
    - env: OPTS="--HEAD"

Possible improvements include running brew audit, and building binary packages, which can be uploaded e.g. to Bintray or attached to a GitHub release.

[ronaldtse]

@skalee I've given you access. Could you help update it? Thanks! 😉

[ronaldtse]

Please help also include the other improvements, they will be definitely useful!

[skalee]

@ronaldtse Travis CI needs to be enabled for https://travis-ci.org/riboseinc/homebrew-rnp.

[ronaldtse]

@skalee done!

[skalee]

Building binary packages extracted to a separate issue #7.

[skalee]

Running brew audit seems to take forever. No idea why. Extracted to #8.