Merge branch 'toc-subpart' into merge-upstream
First stab at appendices for regs E and Z - this uses a relatively flat model
Simplify interpretation titles
Tests for appendix parsing
Merge branch 'appendix' into appendices
Strip tags from appendix headers, too
Merge pull request #130 from cmc333333/appendices

XML Appendices
Checkpoint commit, incorporating Shashank's changes and some reg Z specific bits.
Use the same stack for interpretations levels. Only allow certain collapsed markers. Account for incorrectly emphasized paragraph markers
Cleanup checkpoint
Interpretations parsing cleanup + tests
PEP 8
Fix bug where collapsed paragraph markers weren't being segmented in the text
Merge pull request #131 from cmc333333/xml-interp

XML Interpretations
Merge pull request #132 from cmc333333/collapsed-regtext-italics

Fix bug with collapsed xml paragraph tags