Expose the contents of the mif file as a string

[swapneelap]

To address the issue #139 , @fangohr and @lang-m suggested that:

• We add a method to the driver class which returns the contents of the mif file for the simulation set up as a string.
• Have an argument in the drive method for a "dry run" of the simulation which creates a mif file without running the simulation.

Personally, I am leaning towards returning the string. We can use regex to test it later maybe (?).