* update to leveldb-1.18 and snappy-1.1.2
* update the freebsd/snappy-stubs-public.h to snappy-1.1.2
* update linux/snappy-stubs-public.h to snappy-1.1.2
* try to resolve the travisCI can not build error.
* try to resolve the travisCI can not build error.
* test for TravisCI[build error]
+ UINT32_MAX ifndef this for travisCI
* remove test trap code for TravisCI
+[feature] get sync if no callback
+ put and del can be sync now.
+ batch can sync if no callback
* [bug] memory leak fixed
+ approximateSize sync if no callback
- remove old versions: leveldb-1.17.0 and snappy-1.1.1
Merge branch 'leveldb-1.18_with_snappy1.1.2' into feature/sync
+ readOptions,writeOptions to Database for sync
+ open sync if no callback
+ benchmark sync
+ {asBuffer:false} benchmark test
+ openSync, putSync, getSync, delSync, batchSync
* minor bug fixed
* optimal iterator performance
+ nextSync, endSync on iterator
* some memleak fixed