added history.back method

Added this so that the router is not directly relying on the
window.history object
Merge pull request #232 from tommck/upstream

added history.back method
Added system.isPromise and enabled promise conversion in observable.

The observable plugin will now detect promise properties, wire
callbacks, replace them with observables and update their values when
the async task completes.
Making the router.reset remove all event handlers.
Fixing the minimum required jquery version.
Fixed "pack" and "package" pointing to non-existent "package" instead of "pack".
Merge pull request #233 from thinkloop/master

Fixed "pack" and "package" pointing to non-existent "package"
Modal dialog models now receive detached callback.

Removed api docs from source.
Ensuring that generated api docs are not included in source.
Optional param replaceRoute added to mapUnknownRoutes...

...this allows the developer to easily specify a module *and* a route to
replace the url with when an unknown route is encountered.
Ensuring no bom on dist lib.
Better error messages for script load failures.

This is related to durandal's own internal use of system.acquire, which
it now has proper fail handlers for throughout.
BREAKING CHANGE viewModelBinder renamed to binder.

-Some improvements to api docs added.
Accounting for IE10 bug in log.error.
Fixes to error reporting throughout.
Fixed bug in observable dependencies.
Fixing a promise issue.

The last issue related to returning multiple values from a promise. Not
all promise implementation support this, so the activator had to be
changed to store lifecycleData on the settings object for
canActivate/canDeactivate calls that return instruction objects to be
interpreted by the specific activator.
Intercepting a tags when push state is active.
Don't try to navigate to a route when clicking an 'a' tag that starts with a hash (with pushState enabled)
Merge pull request #238 from csantero/master

Don't try to navigate to a route when clicking an 'a' tag that starts with a hash (with pushState enabled)