Tabs for files #190

Motivation
I don't like repeating to open menu and open different file and it's a struggle for me (or everyone) since there is no other way to make it easy at this version.

Description
Add a file tabs which display all files from current directory and just like the menu, add a feature that everytime I select other file, no confirmation dialog saying to save the file. just temporarily save the file content even it's not completely saved.