Merge pull request #61 from mapbox/kdz-print-jvm-exception

Print JVM exception in template method as well

Let JVM print an exception and a backtrace of the stack. (#53)

promote UntaggedType constructor to public (#52)

Modify GetAttachedEnv() to detach thread automatically. (#51)

Add GetAttachedEnv function. (#50)

Thow IllegalStateException if native peer is dead. (#49)

add overwritable <jni/string_conversion.hpp>

Rationalize New* ref-creating methods

Rename Tagged → Unique, move to own file

Simplify UntaggedType<T>

Array and Class inherit from Object

Remove implicit pointer conversions

Fix derived → base conversions

Fix boxed type inheritance