Update .gitignore and remove app.iml from version control

Author: jacob-tabak

.gitignore

@@ -81,7 +81,7 @@ proguard/
 ### Intellij ###
 # Covers JetBrains IDEs: IntelliJ, RubyMine, PhpStorm, AppCode, PyCharm
 
-/*.iml
+*.iml
 
 ## Directory-based project format:
 .idea/