Allow to rename basename for PNG in ZIP export option.

[posva]

When using texturepackers the name of the file is important as it will be used to generate data.

Currently pixel names all png exported in ZIP to sprite_x.png. I wanted to use the #save-name field but I realized your current setup is not saving text inputs so I added one.

Tell me what do you think about it and feel free to change the text I added.

[juliandescottes]

Thanks ! Looks good, I'll merge this later today.

(Don't worry about the travis build failing, it's not related to your pull request)

[posva]

I actually tested it with grunt test and saw it was failing with the same error as for the last travis build so I thought there are some issues with testing at the moment :P
I'm glad it helps 😄

[juliandescottes]

Sorry, I didn't merge your PR yet :(

I was thinking that we could reuse the name of the piskel (cf ns.PngExportController.prototype.getPiskelName_) as the default value for the prefix ? instead of the current 'sprite_' ?

Of course this only works for saved piskels (either in local storage or on piskelapp.com ).

[juliandescottes]

Merged to master !

[posva]

Hey sorry for not answering you reply xD I didn't have quite the time to do it. So yeas, do as you please, I also think it fits better, I just used sprite_ because it was the previous behaviour ^^

[posva]

Also congrats forp making the tests run again :P

[juliandescottes]

No worries :) thanks for the contribution ! (I slightly shortened the help text in the final version for info)