Make JavaScript client work in both Node.js and browser

* Replace jQuery with SuperAgent which works in both Node.js and browser
* Use UMD pattern (returnExports.js) to make the module exporting compatible
  with all major systems: AMD, Node.js (CommonJS) and browser
* Implement support of header and form parameters. Closes #1736
* Move HTTP requesting code to `ApiClient` and allow customizing options
  in it, e.g. "basePath"
* Update unit tests accordingly and add some tests for `ApiClient`

modules/swagger-codegen/src/main/java/io/swagger/codegen/languages/JavascriptClientCodegen.java

@@ -133,6 +133,8 @@ public class JavascriptClientCodegen extends DefaultCodegen implements CodegenCo
         typeMapping.put("double", "Number");
         typeMapping.put("number", "Number");
         typeMapping.put("DateTime", "Date");
+        // binary not supported in JavaScript client right now, using Object as a workaround
+        typeMapping.put("binary", "Object");
 
         importMapping.clear();
     }
@@ -205,6 +207,7 @@ public class JavascriptClientCodegen extends DefaultCodegen implements CodegenCo
 
         supportingFiles.add(new SupportingFile("package.mustache", "", "package.json"));
         supportingFiles.add(new SupportingFile("index.mustache", sourceFolder, "index.js"));
+        supportingFiles.add(new SupportingFile("ApiClient.mustache", sourceFolder, "ApiClient.js"));
     }
 
     @Override