[refactor] Moved AttributeBuilder out of properties (5m)
[refactor] Refactored Break element to use Attribute Builder (15m)
[refactor] Moved to_xml to the Element base class (1m)
[refactor] Refactored the Symbol element (5m)
[refactor] Allowed overriding an attribute's default namespace (1m)
[refactor] Refactored the text element to use AttributeBuilder (5m)
[skip] Added rake alias for `be rake test` to point to `be rake` (1m)
[refactor] Refactored Paragraph and Run to use attribute builder (5m)
[improvement] Added content_part element (2m) [#19c]
[skip] Added exception if attribute has uses a reserved name

Reserved names are:
  - tag
  - name
  - namespace
  - properties_tag

Without this, declaring an attribute with one of these names leads to a pretty inscrutable error :'(
[improvement] Added the control element (10m) [#19d]
[improvement] Added the carriage return element (2m) [#19e]
[improvement] Added the shortDay element (2m) [#19g]
[improvement] Added the longDay element (2m) [#19f]
[improvement] Added ruby container (3m) [#19y]
[improvement] Added the hps property (10m) [#19k]
[improvement] Added the hpsBaseText property (10m) [#19l]
[improvement] Added the hpsRaise property (10m) [#19m]
[improvement] Added the lid property (5m) [#19o]
[skip] Improved error message for invalid value properties (1m)