Excluded local project files and build output

- Updated .gitignore for project files per IntelliJ guidelines:
https://intellij-support.jetbrains.com/hc/en-us/articles/206544839-How-to-manage-projects-under-Version-Control-Systems
- Eliminates spurious changes to project files from Android Studio automatic changes.

Author: David Collins

.gitignore

@@ -1,6 +1,10 @@
 .DS_Store
 
-.idea/dictionaries
+.idea/shelf
+
+.idea/tasks.xml
+
+.idea/workspace.xml
 
 build