feat: update to Linter v2 API

Update to the v2 Linter API, allowing this provider to continue working 
with recent builds of linter.

lib/index.js

@@ -17,6 +17,7 @@ let disableWhenNoHtmlhintConfig;
 
 // Internal variables
 const phpEmbeddedScope = 'text.html.php';
+const validSeverities = ['info', 'warning', 'error'];
 
 // Internal functions
 const getConfig = async (filePath) => {
@@ -111,7 +112,7 @@ export default {
       name: 'htmlhint',
       grammarScopes: this.grammarScopes,
       scope: 'file',
-      lintOnFly: true,
+      lintsOnChange: true,
       lint: async (editor) => {
         if (!atom.workspace.isTextEditor(editor)) {
           return null;
@@ -146,12 +147,20 @@ export default {
           return null;
         }
 
-        return messages.map(message => ({
-          range: generateRange(editor, message.line - 1, message.col - 1),
-          type: message.type,
-          text: message.message,
-          filePath
-        }));
+        return messages.map((message) => {
+          let severity = message.type.toLowerCase();
+          if (!validSeverities.includes(severity)) {
+            severity = 'error';
+          }
+          return ({
+            severity,
+            excerpt: message.message,
+            location: {
+              file: filePath,
+              position: generateRange(editor, message.line - 1, message.col - 1)
+            }
+          });
+        });
       }
     };
   }

package.json

@@ -91,12 +91,12 @@
     }
   },
   "package-deps": [
-    "linter"
+    "linter:2.0.0"
   ],
   "providedServices": {
     "linter": {
       "versions": {
-        "1.0.0": "provideLinter"
+        "2.0.0": "provideLinter"
       }
     }
   },

spec/linter-htmlhint-spec.js

@@ -24,10 +24,10 @@ describe('The htmlhint provider for Linter', () => {
     const messages = await lint(editor);
 
     expect(messages.length).toEqual(1);
-    expect(messages[0].type).toBe('error');
-    expect(messages[0].text).toBe('Doctype must be declared first.');
-    expect(messages[0].filePath).toBe(badFile);
-    expect(messages[0].range).toEqual([[0, 0], [0, 5]]);
+    expect(messages[0].severity).toBe('error');
+    expect(messages[0].excerpt).toBe('Doctype must be declared first.');
+    expect(messages[0].location.file).toBe(badFile);
+    expect(messages[0].location.position).toEqual([[0, 0], [0, 5]]);
   });
 
   it('finds nothing wrong with a valid file (good.html)', async () => {