translate Paths to valid dot-separated MongoDB collection names (Fixes #139)
improve handling of nested paths
move much of the path wrangling into mongodb.filesystem
simpler path<->collection name translation
escape '$' in collection names
cleanup
simplify result type for ls()
Merge pull request #144 from mossprescott/139-nested-paths

translate Paths to valid dot-separated MongoDB collection names (Fixes #139)