tweaked doctest
do not require numpy for MutableProbDist and do not exit in case of failure
fixed Boxer interface to work with latest revision of svn Boxer
support the `alfa` predicate from Boxer
Merge pull request #325 from kmike/fix-MutableProbDist

I think MutableProbDist shouldn't require numpy and shouldn't exit in case of failure
Fixed comparisons for Python 3.
- replaced `__cmp__` with `__eq__`, `__ne__` and `__lt__`, and `@total_ordering`
- added `__hash__` whenever `__eq__` is defined (new py3 semantics for `__hash__`)
- replaced `cmp` keyword argument with `key` in calls to `sort`/`sorted`
- different types should not in general be orderable, so `__lt__` raises a TypeError in these cases (exception: Tree and FeatStruct)
Renamed `next` method for chart edges to `nextsym` -- edges are not iterators, so `next` is an unfortunate name
Fixed integer division for Py3
Added a "text" format to `nltk.data.load`, returning a unicode string.
Replaced `isinstance(x,str)` with `isinstance(x,string_type)`
Added optional text encoding argument to several functions for string parsing and file reading.
Removed hard-coded file path in `GlueDict`, and used `nltk.data.load` for reading the glue file instead.
Doctest fixes: replacing sets with sorted lists, fixing the number of decimals, etc.
DRT pretty-printing
Minor fixes to `sourcedstring`
pass instead of print
doctests that are not failing anymore!
Merge pull request #328 from heatherleaf/2and3

Fixing `__cmp__` for 2and3
Various fixes: remove some "except:" usages; use "with"; fix unresolved attributes.
revert incorrect skolemize fix