Lsframe

First release of lsframe, formerly released as lrengine

- Fixed bug that caused some folders to be missed when mapping directories
- Improved handling of empty folders and hidden folders/files

- Added ability to define classifiers and function_args in the drive() call

* Added map_to_frame() method
* bug fixes, updated docs, updated unittests

* Added on_date() and in_range() methods for narrowing the dates to specific dates or ranges
* Added "only_unique" option to reduce_dates() for keeping only unique dates when lists
* Added "null" output for function errors in engine
* Renamed "names" column of frame to "name" for consistency with other columns
* updated examples, documentation, unittests, and fixed some bugs

* Expanded date parsing to look for all possible combinations of number sequences
* Expanded find_dates() and reduce_dates() accordingly to deal with lists
* Expanded the list of date formats that can be found
* Improved pattern searching with dict
* Fixed bug in engine
* Fixed missing 's' parameter in sea()
* Improved exception handling