fix travis.yml format

doc/dart-target.md

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+# ANTLR4 Runtime for Dart
+
+### First steps
+
+#### 1. Install ANTLR4
+
+[The getting started guide](https://github.com/antlr/antlr4/blob/master/doc/getting-started.md) 
+should get you started.
+
+#### 2. Install the Dart ANTLR runtime
+
+Each target language for ANTLR has a runtime package for running parser 
+generated by ANTLR4. The runtime provides a common set of tools for using your parser.
+
+Install the runtime with Composer:
+
+```bash
+composer install antlr/antlr4
+```
+
+#### 3. Generate your parser
+
+You use the ANTLR4 "tool" to generate a parser. These will reference the ANTLR 
+runtime, installed above.
+
+Suppose you're using a UNIX system and have set up an alias for the ANTLR4 tool 
+as described in [the getting started guide](https://github.com/antlr/antlr4/blob/master/doc/getting-started.md). 
+To generate your Dart parser, run the following command:
+
+```bash
+antlr4 -Dlanguage=Dart MyGrammar.g4
+```
+
+For a full list of antlr4 tool options, please visit the 
+[tool documentation page](https://github.com/antlr/antlr4/blob/master/doc/tool-options.md).
+
+### Complete example
+
+Suppose you're using the JSON grammar from https://github.com/antlr/grammars-v4/tree/master/json.
+
+Then, invoke `antlr4 -Dlanguage=Dart JSON.g4`. The result of this is a 
+collection of `.Dart` files in the `parser` directory including:
+```
+JsonParser.Dart
+JsonBaseListener.Dart
+JsonLexer.Dart
+JsonListener.Dart
+```
+
+Another common option to the ANTLR tool is `-visitor`, which generates a parse 
+tree visitor, but we won't be doing that here. For a full list of antlr4 tool 
+options, please visit the [tool documentation page](tool-options.md).
+
+We'll write a small main func to call the generated parser/lexer 
+(assuming they are separate). This one writes out the encountered 
+`ParseTreeContext`'s:
+
+```Dart
+import 'packages:antlr4/antlr4.dart';
+import 'P';
+
+class TreeShapeListener implements ParseTreeListener {
+    void visitTerminal(TerminalNode node) {}
+    void visitErrorNode(ErrorNode node) {}
+    void exitEveryRule(ParserRuleContext ctx) {}
+
+    void enterEveryRule(ParserRuleContext ctx) {
+        print(ctx.text);
+    }
+}
+main () {
+}
+
+$input = InputStream::fromPath($argv[1]);
+$lexer = new JSONLexer($input);
+$tokens = new CommonTokenStream($lexer);
+$parser = new JSONParser($tokens);
+$parser->addErrorListener(new DiagnosticErrorListener());
+$parser->setBuildParseTree(true);
+$tree = $parser->json();
+
+ParseTreeWalker::default()->walk(new TreeShapeListener(), $tree);
+```
+
+Create a `example.json` file:
+```json
+{"a":1}
+```
+
+Parse the input file:
+
+```
+dart json.Dart example.json
+```
+
+The expected output is:
+
+```
+{"a":1}
+{"a":1}
+"a":1
+1
+```