Removed get_data and init_data, changed TimeData.initialize()

[vincepandolfo]

This PR tries to address some of the problems discussed in issue #71 .

• It is now possible to initialize TimeData objects using an initializer function. (Note: This is also the only way to initialize them if save=True). test_save.py has been modified to demonstrate this.
• Removed get_data and init_data

[FabioLuporini]

So the only thing that I can think of (the rest is OK) is that the initializer function could be provided directly through the constructor. Is this still correct ?

[mlange05]

Looks good to me. I would like to add the initializer function to the constructor, although that's not a critical requirement.

[navjotk]

Do you want to use the % operator here to make sure this works even if the number of timesteps above is changed? That would also make the code more self-explanatory.

[FabioLuporini]

Now it is in the constructor. Good

[navjotk]

Merged