Alpha Doesn't Always Go to 1.0f

[higueraalfredo]

Started swiping back and forth after you mentioned how it could lead to problems #82 (comment) and noticed that the alpha wasn't always being fully reset back to 1.0 and sometimes it seems like it gets stuck at 0. Swiping a little to the left/right takes things back to normal.

I downloaded the latest version (2.1.7) and recorded these while running the second example as the first one has the alerts popping up and makes it hard to demonstrate the swiping.

gfycat showing page disappearing: http://gfycat.com/SolidGregariousKouprey#?speed=0.5

alpha getting set somewhere between 0 and 1
http://gfycat.com/OrneryUnequaledFlycatcher?speed=0.5

[sirdharma]

I wrote a fix for that a while ago. Will submit a PR.

[mamaral]

@sirdharma Awesome, thank you!