Properly copy graphics states

[dmarkow]

GraphicState's initializer was properly using dup to copy color_space from previous_state, but it was not using dup on the dash attribute, keeping dash tied to the previous state's dash.

Also added an initialize_copy method to make sure those two attributes are properly copied whenever we dup/clone a graphic state.

Added specs for both updates.

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This somewhat helps with #473 because it makes sure the graphics state is truly immune to any changes after setting a repeater. However, for the time being, a repeater still has to be defined before anything else to ensure a clean slate.

[practicingruby]

Thanks! I made the copying a little more thorough ( 255cc70 ), but they should still do what you want them to.

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Thanks again for the patch!

[dmarkow]

Whoops, I completely spaced on the fact that strings are mutable. Duh.

The immutable objects shouldn't need to be specifically copied within the initialize_copy method, since calling something like @graphic_state.dup already copies all the attributes. The initialize_copy method is only to do something different than the default (in this case, to dup the mutable attributes). Or maybe you added them since you're now calling initialize_copy directly from the main initialize method?

Just want to make sure I'm not missing something. Thanks for merging!

[practicingruby]

You're right, it's probably not necessary to reset those if we were just using this for affecting dup. But since we also call it directly, I suppose it's better to be explicit and set all attributes. I think this code is a candidate for refactoring in general, but I'm not sure we need to address that issue right now.