add "upload" functionality and "replace" functionality
Created by: liyakun
Functions to add new file to current repository and replace the existing file in current repository are added.
Update show.html.haml
add 'upload' view
Update _tree.html.haml
add 'upload' button
Create _upload.html.haml
show upload window
Update file_action.rb
allow user to upload both base64 file and text file
Update _actions.html.haml
add replace action button
Update show.html.haml
add replace (update) view
Create _update.html.haml
show update window
Update CHANGELOG
