Remove .bat file.

Composer is supposed to deal with this automatically.
Merge pull request #169 from platformsh/remove-bat-file

Remove .bat file.
Validate the SSH public key file before attempting to add it.
Fix wrong confirm delete action in drush-aliases command.
Refactor Git commands into a new GitHelper.
Add some functional tests for GitHelper.
Cleanup
Allow toolstacks to write to $output and use shell abstractions.
Merge pull request #174 from pjcdawkins/validate-ssh-key

Validate the SSH public key file
Make toolstack detection error less scary - addresses #173
Fix double error output from shell commands.
Merge pull request #167 from pjcdawkins/git-helper

Refactor Git/shell/Drush commands; and let toolstacks write output
Update tests now that ShellHelper throws a generic exception.
Don't symlink settings.php; copy and warn.
Merge pull request #176 from pjcdawkins/issue/175/settings-php-symlink

Don't symlink settings.php; copy and warn.
Accommodate multiple details in Platform.sh API errors.
Fix: flags (e.g. --yes) not getting passed to Drush make.
Increase timeout for shell commands.
Prevent writing config multiple times.
Remove responseClass from service descriptions.