* 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