2.0.1: Misc fixes (#866)
* misc fixes: 1. TWString leaking in JNI 2. cocoapods build from source 3. split AnySigner.swift (like Java implementation) * revert JNI change, will create a new branch
* misc fixes: 1. TWString leaking in JNI 2. cocoapods build from source 3. split AnySigner.swift (like Java implementation) * revert JNI change, will create a new branch