Restructured shim's patch method if/else logic and added comments

The shim code is now a closer match to the style of the original OpenJDK code.
The code is a little more complex with added if/else nesting, but allows for better explanatory comments.
Update readme with 0.9.1 release coordinate for jCenter
Bump source version to next SNAPSHOT
Fix patch and test suite for edge cases that are expected to differ between JDK 7 and 8 (JDK-7131459)
Prepare for upstream JDK8 fix; don't patch if the HALF_UP and HALF_DOWN cases jump to the same point.
Bump version to 0.9.3-SNAPSHOT, wait for release until JDK patch is finalized.
Version 1.0 - verified with early access release of Oracle Java 1.8.0_40-b12