[styleguide] added api and filename sections

STYLEGUIDE.md

@@ -773,41 +773,36 @@ When creating a utility function, attach it as a lodash mixin.
 
 Several already exist, and can be found in `src/kibana/utils/_mixins.js`
 
-## Modules
-
-Kibana uses AMD modules to organize code, and require.js to load those modules.
-
-Even Angular code is loaded this way.
-
-### Module paths
+## Filenames
 
-Paths to modules should not be relative (ie. no dot notation). Instead, they should be loaded from one of the defined paths in the require config.
+All filenames should use `snake_case` and *can* start with an underscore if the module is not intended to be used outside of it's containing module.
 
 *Right:*
-
-```js
-require('some/base/path/my_module');
-require('another/path/another_module');
-```
+  - `src/kibana/index_patterns/index_pattern.js`
+  - `src/kibana/index_patterns/_field.js`
 
 *Wrong:*
+  - `src/kibana/IndexPatterns/IndexPattern.js`
+  - `src/kibana/IndexPatterns/Field.js`
 
-```js
-require('../my_module');
-require('./path/another_module');
-```
+## Modules
+
+Kibana uses WebPack, which supports many types of module definitions.
 
 ### CommonJS Syntax
 
-Module dependencies should be loaded via the CommonJS syntax:
+Module dependencies should be written using CommonJS or ES2015 syntax:
 
 *Right:*
 
 ```js
-define(function (require) {
-  var _ = require('lodash');
-  ...
-});
+const _ = require('lodash');
+module.exports = ...;
+```
+
+```js
+import _ from 'lodash';
+export default ...;
 ```
 
 *Wrong:*
@@ -824,7 +819,7 @@ Kibana is written in Angular, and uses several utility methods to make using Ang
 
 ### Defining modules
 
-Angular modules are defined using a custom require module named `module`. It is used as follows:
+Angular modules are defined using a custom require module named `ui/modules`. It is used as follows:
 
 ```js
 var app = require('ui/modules').get('app/namespace');
@@ -872,7 +867,7 @@ require('ui/routes')
 
 # Html Style Guide
 
-### Multiple attribute values
+## Multiple attribute values
 
 When a node has multiple attributes that would cause it to exceed the line character limit, each attribute including the first should be on its own line with a single indent. Also, when a node that is styled in this way has child nodes, there should be a blank line between the openening parent tag and the first child tag.
 
@@ -888,6 +883,38 @@ When a node has multiple attributes that would cause it to exceed the line chara
 </ul>
 ```
 
+# Api Style Guide
+
+## Paths
+
+API routes must start with the `/api/` path segment, and should be followed by the plugin id if applicable:
+
+*Right:* `/api/marvel/v1/nodes`
+*Wrong:* `/marvel/api/v1/nodes`
+
+## Versions
+
+Kibana won't be supporting multiple API versions, so API's should not define a version.
+
+*Right:* `/api/kibana/index_patterns`
+*Wrong:* `/api/kibana/v1/index_patterns`
+
+## snake_case
+
+Kibana uses `snake_case` for the entire API, just like Elasticsearch. All urls, paths, query string parameters, values, and bodies should be `snake_case` formatted.
+
+*Right:*
+```
+POST /api/kibana/index_patterns
+{
+  "id": "...",
+  "time_field_name": "...",
+  "fields": [
+    ...
+  ]
+}
+```
+
 # Attribution
 
 This JavaScript guide forked from the [node style guide](https://github.com/felixge/node-style-guide) created by [Felix Geisendörfer](http://felixge.de/) and is