Nonexistent export paths are created during SKY query
Empty XML file generates empty XML element

Appending new elements still has to be implemented
SkyQuery can deals with missing read_element
Refactor find_field_element_text() into __getattr__

Simplifies class' outward facing interface a bit
Refactor set_field_element_text() into __setattr__()

This also simplifies the outward facing interface
SkyQuery can create read_element if needed
Move logic for creating read, select elements into __getattr__

This way if I look for an element that isn't there, it's created properly.
Also, if I try to set an element that isn't there, it's set correctly.
Refactor redundant read-or-create logic in __getattr__
Cleanup lookup logic
Logic for working with nonexistent reference dates
field_elements searches only in select element
Use LXML's get method rather than manually parse dictionary
Rework logic for working with potentially nonexistent elements

get_or_create_element() did not require direct access to the object's fields,
so I refactored it to be a class method for clarity.

Almost all fields can now be handled from an empty call.
Simply attribute lookups by using get method
Refactor get_or_create_element to deal with multiple entries

This was required in order to be able to modify the transfer element,
which is a sibling to the select element. Before I was returning the
first element found when searching the read element. Now I return the
first element that *matches the query.* This allows me to differentiate
between possible different sibling types without requiring a separate
scheme for the transfer element.
Rework lookup logic for multiple elements
Add test for read SkyQuery
Merge branch 'query1'
Merge branch 'master' into generate_xml
Add test for settables in generated queries