add gitattributes (#2017)

* build(composer): add archive

* chore(gitattributes): add .gitattributes

.gitattributes

@@ -0,0 +1,13 @@
+* text=auto
+
+/.github export-ignore
+/bower_components export-ignore
+/build export-ignore
+/documentation export-ignore
+/pages export-ignore
+/plugins export-ignore
+.gitattributes export-ignore
+.gitignore export-ignore
+index.html export-ignore
+index2.html export-ignore
+starter.html export-ignore

composer.json

@@ -25,7 +25,6 @@
     "issues": "https://github.com/almasaeed2010/AdminLTE/issues"
   },
   "require": {
-    "composer/installers": "1.*",
     "bower-asset/jquery": ">=1.9.0 <4.0.0"
   }
 }