Crash when removing inactive touches

[toddreed]

This was reported in a comment by @gatamar for #16, but I think it’s a separate bug.

The issue is with line 85:

Touchpose/Pod/Source/TRTouchposeApplication.m

Lines 80 to 86 in dd2b729

	void const * keys[count];
	void const * values[count];
	CFDictionaryGetKeysAndValues(_touchDictionary, keys, values);
	for (CFIndex i = 0; i < count; ++i)
	{
	UITouch *touch = (__bridge UITouch *)keys[i];

which would attempt to retain an object that may no longer exist.