Print out the task method signature when `fab -d <task_name>`.
Calculate args_without_defaults from args_with_defaults.
Add tests for task details.
Monkey-patch inspect.getargspec for Python 2.5

because the return type changed from plain tuple to namedtuple since 2.6
Merge branch 'master' into 922-int
Failing test re: wrong indents in multiline docstrings
Bring the indentation of the added detail to the same level of docstring

so that the docstring and the method signature are uniformly indented.
Tweak test for accuracy
Docstring re #922