Add initial version of IMPL.txt document
Merge branch 'master' of github.com:brownplt/lambda-py into multiple_inheritance
Merge branch 'master' of github.com:brownplt/lambda-py into multiple_inheritance
add PyImport and desugar to assigment [issue #2]
add IMPL file to module test
Update implementation documents
add PyImportFrom in surface syntax and get-strcutured-python; havn't desugar yet [issue #3]
desugar PyImportFrom [issue #3]
Update implementation document
desugar from x import * [issue #4]
Merge branch 'modules' of github.com:brownplt/lambda-py into modules
Implemeted builtin-type file. (closes #16)
Added notes to IMPL
Made globals a mutable hash.

By doing this we can't have CLet work on the global scope. Added a new
local env when CLet is used in global scope as a work-around, assuming
that there won't be any local bindings in let-body.
Change base to bases
Initial changes for multiple inheritance: base changed to bases,
but kept as list of symbols, not tuple of classes as it should be
to be able to implement type(name, bases, dict).
Adapted test_mro_disagreement.py to use class statement instead of
type(name, bases, dict).
Temporarily implemented type(obj) as a function, not an object.
Fixed error in ___fail() to match py-prelude.py
Add mk-type function for class creation
for now the bases tuple is used only for antecedent computation...
Add mro calculation
The tuple of bases was added as __bases__ field to class dict
__mro__ is not finished, due to the use of immutable hashes for
class dict I'm thinking to not include the class itself as first
element and to prepend it at mro retrieval.
Add __mro__ attribute to classes
Passes the tests related to __mro__ construction, both positive and
negative cases.
__mro__ attribute doesn't contain the own class yet.
Use __mro__ for field lookup
get-field was modified to use __mro__ for class hierarchy navigation and
to special-case __mro__ attribute retrieval, to avoid self-reference.
Pass all python-reference tests and 5/7 multiple_inheritance tests.
isinstance and super do not implement multiple inheritance yet.
enabled multiple inheritance on isinstance
all python-reference tests continue working.