* add more code for parsing boolean queries

LOL this shit is going to break like fck in testing.
* fix syntax for declaring static methods
* fix merging, tests for merging
* add todo list
* minor fix for merge_results
* minor fix for tree construction (doubt it works yet)
* parser:
  - added __str__/__repr__ methods for printing
  - fix regexp groups being used
  - fix the iteration invariant (return False as
  necessary)--investigate further, might be unnecessary)

* search: fix the merging for OR (sort _after_ making the keys unique,
  as the process of making them unique isn't stable)

* tests:
  - add logging
  - add tests to ensure that creation of simple trees *works*
    + they don't test yet whether the *correct* trees are created
* fixed the left vs right in the string representation of a tree
* parser:
  - fixes in creation of "(...)"
  - fixes when only one of "... () ..." exists

* tests: add equality checks for the trees being tested
* parser:
  - add bunch of logging calls
  - modify conditions to ensure that whitespace isn't taken to
  indicate presence of content
* tests: added tests for paranthesis
* add comments to parser
* modify merge_results to return SkipLists instead of []
* modify tests to expect SkipLists returned from merge_results
added in sample data
* 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
Fix merging to use skip pointers
* add essay answers
* add backup copy of the output