Changed zooming behaviour.

Nodes and eges maintain their size.

Probably should be an option
Implemented 2 zooming behaviours.

By default, nodes and labels keep their size. The
"normal" zooming is performed when the shift key
is pressed while zooming.
Fixed variable name
Correct comments and default behaviour
Fixed info output
Added new targets
Cleanup
Updating .gitignore
Fixes #1
Fix in_edges_iter with data
Changes SpecRunner and test execution.

Instead of having a fixed SpecRunner.html and SpecRunner_compiled.html
file, an ant task is now generating a SpecRunner.html from a template.

The script test_collect.py goes through all directories and finds all
test files in "tests" directories.

Some tests define classes used by other tests (e.g. jsnx/classes/tests).
To ensure the correct loading order, a running index has been added to
these file names.

To build SpecRunner.html, run "ant prepare.test".
To test the compiled version, run "ant test_compile" which will now run
"ant prepare.test" in addition to compiling the code.
Adds range, permuations and combinations generators.
Adds classic generator functions.

Adds the following functions from "generators/classic":

    - complete_graph
    - cycle_graph
    - empty_graph
    - null_graph
    - path_graph
    - trivial_graph

Note: The unit test for path_graph was not ported yet, since it uses
"is_isomorphic" (not implemented yet) which uses a bunch of other stuff.
Adds random generator functions.

Adds the following functions from "generator/random_graphs"
    - fast_gnp_random_graph
    - gnp_random_graph
Updated .gitignore
Ignore changes to jsnetworkx.js if not compiled.
Cleanup SpecRunner_template.html
Adds utils methods.

Adds the following methods from "utils/misc":

    - is_list_of_ints
    - cumulative_sum
    - generate_unique_node
Adds max method with callback.
Fixes combinations and permutations.

They will now correctly return an empty iterator if the size of the
input is smaller than the size of requested combinations/permutations.