Add configuration option to 'fsync' after every tlog modification

Using the new 'fsync' configuration boolean (used in a node
configuration section), an fsync(2) call will be issued after every
modification of a tlog file.

See: ARAKOON-389
See: http://jira.incubaid.com/browse/ARAKOON-389
Merge pull request #79 from Incubaid/ARAKOON-389

Add configuration option to 'fsync' after every tlog modification