sed command in install.sh has wrong syntax for Mac OS X

[jordanlgraham]

Executing the quick-start command:

composer create-project --stability dev --no-interaction --ignore-platform-reqs bradjonesllc/docker-drupal:dev-master PROJECT-DIR

I received an error from sh scripts/composer/install.sh:

sed: 1: ".gitignore": invalid command code .
Script sh scripts/composer/install.sh handling the post-create-project-cmd event returned with error code 1

Seems as though sed doesn't like a filename that begins with a period.

[bradjones1]

@jordanlgraham This works on Linux but not Mac OS X, which appears to be a known issue with sed, not that it doesn't like the hidden-files dot prefix but that it requires different parameters. Open to a PR to fix on Mac.

See: https://stackoverflow.com/questions/4247068/sed-command-with-i-option-failing-on-mac-but-works-on-linux