Changed the way ID are collected

[Frank3K]

All referenced IDs are collected and mapped to unique IDs. Unreferenced IDs are removed in order to save space and clutter. Furthermore, the md5()-function is only called when really necessary which leads to (micro) time optimizations.

[Frank3K]

I just figured the md5 function is actually called more often now. I will fix this tomorrow.

[Frank3K]

I tried the rebasing as suggested in #42. Now this branch seems to consist of only the commits related to this PR. For some reason I ended up with two times the 'Minor speed improvement...' commit.

What I did was:

• git checkout id-references (i.e. the branch we need here)
• git pull --rebase upstream master (where upstream is the clone URL of your repository)
• git pull (otherwise it did not push)
• git push

Should I clean this up more? By rebasing / squashing commits into a single commit?

[Frank3K]

Could you take another look at this PR? I'm unclear on how to improve this one.

[FWeinb]

Finally got some time to merge all this in thanks for this! 🎆

Would you mind writing a small list of all changes you did feature releated?

[Frank3K]

Thanks for merging the PR's! I'll try to make possible future PR's less cluttered.

The first PR (#39) was solely about style changes, so I don't need to comment on that.

Changes / new features:

• Changed the way ID are collected; unreferenced IDs are removed now in order to save space. (Changed the way ID are collected #40)
• Changed the behavior of the 'cleanup'-option (introduced in 0.2.6). Apart from true / false, the value of this property can now be an array of attributes. All attributes in the array are removed from all elements in the SVG. (Cleanup improvements #41)
• Added an option 'cleanupdefs' (default: false). When set to false, no cleanup is performed on the <defs> element. (Cleanup improvements #41)
• Empty g elements are removed since they have no effect in a document. (Remove empty g elements #42)

[FWeinb]

@Frank3K Thanks 👏 released in 0.3.0