The web thumbnail icon and the note thumbnail icon is now displaying at the right position
fixing the bug that sometimes the web thumbnail icon is not created
Update: Created an array to store all the thumbnail icons, icons are shown at a position which is nearest to the corresponding  text. If the position is taken by another icon, it will search for other free space blow it to avoid conflict.
Fixing the "text fails to update" bug in the github issue list
Update: Implemented a log file method to log student activity with time stamp
Update: Created a LogFileController to control the log activity
Created a xml file writer and reader to store and load the highlight content
saving and reloading the highlight content
Fixing the bug that the background image gets tiled after rotation.
save the web link and the note the user adds.
Fixing the bug that when the program runs the first time on the device, the highlight and thumbnail icons can not be saved because the xml files hasn't been created.
creating a highlight, note review feature.
autosize the content view controller
adding concept map view
adding recourse tag to concept nodes
Saving and loading the concept maps.
Auto save the concept map
highlighting concept nodes
Navigation:
By clicking on each concept node, you can now go to the textbook page where this concept is first added.