[feature] Can change File mode

[bae-jae]

when i use vim editor to edit file the file follow did not work.
because other group have only read authority the file .
So i  added function that can change file mode for other group in Tail class

example1.py didn't work with following file permission

So i added function that this give read, write permissions to other groups

And you could check new file mode Like this

##Reuslt Can now track files no matter what editor they use.

related to #12