Allowed more descriptive module names.
Note they must not have spaces in them; use underscores instead.
Each module (subdirectory in a Course) must have only one .csv file withe the  name "lesson.csv"
Removing renamed files.
module to lesson in content only
changed the rest of the instances of 'module' to 'lesson' in code and directory names
changed a few more instances of module to lesson in file names
a few tweaks so that R CMD check passes
fixed issue with showing pretty lesson names in lesson menu
author_lesson() now creates lesson.Rmd instead of custom-named lesson
updated DESCRIPTION with Sean's name and incremented version to 2.1
fixed rmd2csv.R so that it works with the new more extensive YAML
Merge pull request #75 from ncarchedi/modnames

Changed all instances of 'module' to 'lesson' in code, comments, directories, and file names
added swirl version line to YAML and changed rmd2csv defaults to omnitest
bill's fix for mult_question testing plus a check for comments in corr_ans in rmd2csv
Merge pull request #76 from ncarchedi/master
Merge pull request #74 from seankross/master

improved install_course_url api
added whisker to imports to customize author_lesson() template
Merge pull request #77 from ncarchedi/master

lesson template is now customized via the whisker package
added MANIFEST feature that allows for ordering of courses