test(cli)!: Add test for multiple config options

Note: there was a breaking change that we forgot to document. Ww write the breaking change here for it to be picked up in the future 3.0 release,
even though it was introduced in commit 3871765

BREAKING CHANGE: the CLI no longer accepts "extra options". Instead you should pass the `-c` flag. To update:

before:
```
showdown makehtml -i foo.md -o bar.html --strikethrough --emoji
```

after:
```
showdown makehtml -i foo.md -o bar.html -c strikethrough -c emoji
```

Closes #916

src/cli/cli.js

@@ -52,7 +52,7 @@ program.command('makehtml')
   .option('-a, --append', 'Append data to output instead of overwriting. Ignored if writing to stdout', false)
   .option('-e, --extensions <extensions...>', 'Load the specified extensions. Should be valid paths to node compatible extensions')
   .option('-p, --flavor <flavor>', 'Run with a predetermined flavor of options. Default is vanilla', 'vanilla')
-  .option('-c, --config <config...>', 'Enables showdown makehtml parser config options. Overrides flavor')
+  .option('-c, --config <config...>', 'Enables showdown makehtml parser config options (example: strikethrough). Overrides flavor')
   .option('--config-help', 'Shows configuration options for showdown parser')
   .action(makehtmlCommand);
 

test/node/testsuite.cli.js

@@ -128,6 +128,16 @@ describe('showdown cli', function () {
         proc.stdout.should.equal('<p>this is a 😄</p>');
       });
 
+      it('should enable 2 showdown options (emoji and strikethrough)', function () {
+        var proc = spawnCLI('makehtml', ['-c', 'emoji', '-c', 'strikethrough'], {
+          input: 'this is ~~not~~ a :smile:',
+          encoding: 'utf-8'
+        });
+        proc.status.should.equal(0);
+        proc.stderr.should.contain('Enabling option emoji');
+        proc.stdout.should.equal('<p>this is <del>not</del> a 😄</p>');
+      });
+
       it('should ignore unrecognized options', function () {
         var proc = spawnCLI('makehtml', ['-c', 'foobar'], {
           input: 'foo',