make the `new` operator optional before the `JSZip` constructor

This line of code implements John Resig's self-calling constructor pattern.

See also:

http://ejohn.org/blog/simple-class-instantiation/

http://habrahabr.ru/post/135027/
Fix release date
Fixing more release date

Back to the futur
Merge pull request #95 from 3on/patch-1

Fix release date
+1 test: Constructor adds `new` before itself where necessary
use explicit `instanceof JSZip` check (twice)
Merge pull request #93 from Mithgol/patch-1

make the `new` operator optional before the `JSZip` constructor
update the example to work with IE 10/11
update documentation for blob url

See Stuk/jszip#96 : we still don't have a solid, cross brower way to
download the zip file...
update copyright year
Merge pull request #99 from gdi2290/patch-1

update copyright year
doc : add a note about IE's compatibility view
migration guide : add .asBinary() to the example

Fix issue #100 : the migration guide said that the equivalent of .data
is .asText() but the utf8 conversion is not always welcomed.
use addEventListener instead of onclick

Also use attachEvent as a fallback. This page will only works with
everything but old IE so this fallback will only be useful to display
error messages in IE 8 :)
documentation about the optional `new` operator

See #93 for more informations.
Merge pull request #101 from dduponchel/update_doc

Update documentation