Run eslint from node_modules/.bin rather than node_modules/eslint/bin

Rationale:
- `npm install`, `yarn` and `lerna` all fill out `node_modules/.bin`
- But `node_modules/eslint` isn't necessarily present.
- This should fix issue google#490.

src/cli.ts

@@ -145,7 +145,7 @@ export async function run(verb: string, files: string[]): Promise<boolean> {
     case 'lint':
     case 'check': {
       try {
-        await execa('node', ['./node_modules/eslint/bin/eslint', ...flags], {
+        await execa('node_modules/.bin/eslint', flags, {
           stdio: 'inherit',
         });
         return true;
@@ -156,13 +156,9 @@ export async function run(verb: string, files: string[]): Promise<boolean> {
     case 'fix': {
       const fixFlag = options.dryRun ? '--fix-dry-run' : '--fix';
       try {
-        await execa(
-          'node',
-          ['./node_modules/eslint/bin/eslint', fixFlag, ...flags],
-          {
-            stdio: 'inherit',
-          }
-        );
+        await execa('node_modules/.bin/eslint', [fixFlag, ...flags], {
+          stdio: 'inherit',
+        });
         return true;
       } catch (e) {
         console.error(e);