- TTL do NOT have the ownership of thread local/snapshot!
- more gc friendly, avoid potential memory leak!

- use WeakHashMap type for implementation
  express the weak semantics implicitly
- use keySet instead of entrySet
  simplify the code

- fix javassist link
- move developer material to developer guide

see
https://travis-ci.community/t/solved-oraclejdk8-installation-failing-still-again/3428

- add jdk 11 for appveyor ci
- exclude branch appveyor for travis ci
- fix typo: workaroud -> workaround

- add package-list for spotbugs-annotations
- exclude deprecated TtlEnhanced from javadoc

JSR305 is already Dormant status, so SpotBugs does not release jsr305 jar file.
Please continue using findbugs’ one.
depend on spotbugs-annotations instead.

https://spotbugs.readthedocs.io/en/stable/migration.html

- add spotbugs-maven-plugin
- use spotbugs-annotations instead of jsr305

- protect for NPE in method isAutoWrapper
    - add UT for getting unboxing boolean from map
- rename method/var: setAutoWrapper -> setAutoWrapperAttachment

unwrap ttl runnable for before/afterExecute methods
of executor subclass when decorate by ttl agent

- setAutoWrapper for TtlRunnable/TtlCallable
  in TtlExecutorTransformlet(Agent)
- update before/afterExecute methods of executor subclasses,
  unwrap runnable if isAutoWrapper

should unwrap ttl runnable for before/afterExecute methods of executor subclass
when decorate by ttl agent