fix(lib): Restore original behavior when invoking without any argument

Restore the module's original behavior of interpreting the current package's main script as source
of an eslint config, rather than taking the local package.json's eslintConfig property into account.

bin.js

@@ -17,6 +17,12 @@ if (newRules.length) {
   process.exit(1)
 }
 
+function resolvePackagesMain(cwd, packageFile) {
+  var packageFilePath = path.join(cwd, packageFile)
+  var packageJson = require(packageFilePath)
+  return packageJson.main
+}
+
 function getConfigFile() {
   var specifiedFile = process.argv[2]
   if (specifiedFile) {
@@ -28,7 +34,7 @@ function getConfigFile() {
     }
   } else {
     // this is not being called with an arg. Use the package.json `main`
-    return path.join(process.cwd(), 'package.json')
+    return resolvePackagesMain(process.cwd(), 'package.json')
   }
 }