fix #6 , Latest read feature, cleanup

* Added FileManagers, now different file versions can be read with the same method call. #6
* Seperated concerns: architecture consists of DiaryController, Diary, Entry and FileManager classes.
* Set up `diary read latest` feature
* Set up tests
* added ignore files

.gitignore

@@ -1,4 +1,6 @@
 __pycache__/*
 *.pyc
 diary_config
-diary
+diary
+testdiary
+*diaryback*

README.md

@@ -33,6 +33,13 @@ After having added the .py extension and the program directory to path, the Diar
 >```
 >helps you search for strings in your file. The ```searchall / findall``` also works in a similar fashion except that it fetches those entries that simultaneously have all the search strings in it.
 
+>```
+>diary backup [filename]
+>```
+>creates a backup copy of the diary file.
+
 The `DiaryController` class is responsible for handling user interaction to access the `Diary`.  
 The `Diary` class contains a list of `Entry` instances that contain a record of the user's input.
+The `FileManager` class deals with read and write operations of files.
+`DiaryController` is passed an instance of the `Diary`.