Fix the xml start location of security command line output bug

[niyaoyao]

When I use security cms -D -i embedded.mobileprovision in terminal on my Mac (macOS 10.12.1) it will output an warning string as below
security: SecPolicySetValue: One or more parameters passed to a function were not valid..

Therefore, when I resigned my ipa file it will block at the process of "Entitlements generated".
So, I fix it by finding the xml start location in order to get the correct plist data.

[niyaoyao]

Oh~
After I push a new merge request, I found that several same merge request.

What a pity, cannot be an contributor for iReSign. 🙈

Anyway, it's a excellent tool to resign ipa file.

It was inspired me, and I wanna create a resign tool by myself. Thanks.

[niyaoyao]

Because of you don't merge my branch to project, I create a opensource resign tool project at https://github.com/niyaoyao/EasyResigny.

I am quite confident that it will better than yours, and I will improve the code and experience continuously : )