Rename Result#did_you_means
Shorten Result#tips block to one line
Fix typo in Subpod docs
Add Image element class
Add Image#mime_type

This change adds a method to the Image class that returns the image
MIME type.
Add MathML class

This change introduces a MathML class that adds no additional methods
to its Element superclass. It is there, however, in anticipation of
future methods (like #to_tex).
Add Subpod methods to access other data formats

This change adds Subpod#image, Subpod#mathml, Subpod#plaintext,
Subpod#mathematica_input, and Subpod#mathematica_output. Many of these
methods are dependent on what formats are requested, and will return
nil otherwise.
Move SubpodTest XML to its own file
Make element attributes default to false for bools
Add Text relation

This change adds a DSL for defining methods to access a single
element’s text.
Use Text DSL methods in Subpod
Add empty subpod tests
Rename all relation modules

This change renames all the relation modules by appending “Relation” to
the original module name. This ensures no collision between things like
Relations::Element and Elements::Element.
Remove test namespacing

This is possible because of the previous commit, which ensured that
there are no more name collisions across namespaces.