VanillaChronicle fixes

- Fix for concurrent append in VanillaIndexCache
  Concurrent access to the append method was causing
  a buffer overflow failure because the position was being
  incremented by another thread after the check for end of file.

- Fix for VanillaIndexCache.lastIndexFile
  lastIndexFile method was not listing existing index files

- Fix for VanillaDataCacheTest.testDataForLast
  VanillaDataCache was not listing existing files

- Unit tests for VanillaTailer reading across cycles
Merge pull request #58 from brasslock/master

Fix for concurrent append in VanillaIndexCache
Concurrent access to the append method was causing
a buffer overflow failure because the position was being
incremented by another thread after the check for end of file.

Fix for VanillaIndexCache.lastIndexFile
lastIndexFile method was not listing existing index files

Fix for VanillaDataCacheTest.testDataForLast
VanillaDataCache was not listing existing files

Unit tests for VanillaTailer reading across cycles