* index: dump dict, postings to file
* makefile: add targets for searching, unittests
* search: modify Search class to be initialized from filenames
Full indexing works

* index:
  - set recursion limit to 10000, to deal with the recursive Tree
  structure
  - exception is made for the universal set, which is stored as a
  whitespace delimited string instead

* search: added stemming, case folding
* skiplist: print in format expected by assignment
* makefile: add targets for the IVLE sample queries
* parser: bugfix where whitespace wasn't being stripped out in some
  cases
* search:
  - fix for the sorting behavior that would otherwise cause bad results
  in nested queries
  - manual mode driver
* skiplist: cast value to int when stored