Fix long image scale bug

[phxnirvana]

when scale a long image smaller, it won't zoom back. I found out the reason is mMaxScale smaller than the original scale value.

this commit fix #817 , and i think #408 looks like the same problem

[kele89]

Is there a plan for this to be released?

[jens-muenker]

If you need this fix immediately you can take a look on my fork. I included this fix.

https://github.com/Frosch2010/uCrop-n-Edit