Merge pull request #1 from matelakat/master

Amend readme, custom post install script
Get rid of non-required close statements

As @krisztianfekete mentioned, close() is called upon exiting from the
context.
Merge pull request #2 from matelakat/fix-close

Get rid of non-required close statements
Merge pull request #6 from matelakat/master

Change the order of the parameters
Refactor - create iso module

ISO file related operations moved to a separate module.
Created tempdir_maker module
Refactor - create ubuntu module
Amend Readme