Fix % always 0 in HTML reporter

[AviVahl]

Hi mocha team.
This is a small fix for the progress bar staying consistently at 0 when using the HTML reporter.
Seems like a regression that happened due to the "double-error" fix/refactor.

Reasoning for the changes:
updateStats() accesses this.total, but this === the global object (window) if not specified explicitly here.
Also added a missing update when all tests end.

[boneskull]

can we just use Function.prototype.bind() on updateStats instead?

[AviVahl]

@boneskull Thanks for reviewing.

You could bind updateStats to runner and set it as this.updateStats.
Both approaches would work. You would still need to add a call on 'suite end'.
I wasn't sure if you want updateStats set on the reporter instance here, so I used the a explicit call. Please clarify.

[boneskull]

@AviVahl It looks like updateStats() is always called with the context of the Runner object, so actually call and bind shouldn't be necessary, yes?

[AviVahl]

Calling updateStats() in a block inside a context does not set that context to the call invocation.
I might have an alternative patch which you would like more.
I'll commit.

[AviVahl]

@boneskull new patch allows calling updateStats() directly (without specifying this), as it binds runner to extract the value of total.
Please let me know if this is a nicer solution in your opinion.

[AviVahl]

@boneskull Can we get this small bug-fix reviewed again?
Two lines change for such an annoying UI issue.
Thanks in advance.

[boneskull]

@AviVahl looks good, thanks!