* add fix for the file export code--remove tag tail and text,
  not just the children.

* More tests for mongo modulestore, including tweaks to test files
* add location_to_id method to CourseDescriptors
* Implement path_to_location method in mongo.py
  - TODO: does not handle position in sequences yet.
* fix bug in jump_to view.

* Clean up test data for simple, toy courses
* clean up test_mongo.py
* write initial test for path_to_location
* hook up view to use path_to_location

Next: actually implement it :)

* fix up toy course to match current format
* fix github sync test that referred to toy course

* catch exceptions and return a 404 if course not found
* add Location.is_valid(), tests
* stub of jumpto/ view.

In response to spending an hour with a strange argument passing bug that neither I nor Cale could figure out.

* pass all arguments explicitly
* pass arguments in a consistent order between classes

* change custom tags in test/data/full to new single-tag format
* fix broken file references
* fix argument to import_from_xml
* error_handler fix in mongo.py in next commit

* uses xml modulestore, and new error_handler hook

* no more __xmltree.

* create split_to_file() function
* chapters, html, problems always split
* course never split
* others based on size of subtree for now

* add error_handler member to DescriptorSystem
* call it where import errors happen
* also includes some refactoring in xml.py
* some more line length and docstring cleanups

* no functionality changed in this commit.

Add optional hide_from_toc attribute to XML elements

Kimth/lms coderesponse

Adding the ability for javascript from problems to execute more intelligently

Adding the ability for javascript from problems to execute more intelligently; for example, errors from javascript included in the returned html will show up in the console when using this mechanism.

Compiling coffee files in course data directories on startup.

Add field-error class to field with issues.

Add optional hide_from_toc attribute to XML elements to support Tutorials (which don't show up in the navigation).

* We do not want to disable existing loggers when setting up our own