Merge pull request #20 from nfrancois/saveFuture

Save and remove methods from Persitent object should return Future
Bugfix for PersistentObject remove()
v0.1.3
Upgrade for M4 changes. Obectory server now does not log messages my default, verbosity switched by command line parameter --verbose
v0.1.4
count() method implemented on all platforms, test case added
v0.1.5
Upgrade for Dart SDK version 0.4.7.5_r21658 (post M4)
v0.1.6
PersistentList inherit from ListBase. No more notimplemented methods and type warnings.
v0.1.7