Unit tests for YamlTokenizer.
 Add decorator for main functions (initialize logging and provide command line options)
 New version of scheduler for simple Abinit calculations based on apscheduler.
 Use external file to save the overall number of nodes created (used for __hash__)
 Fix errors in PyFlowsScheduler.
 Start to refactor Strategy objects
Merge branch 'master' of https://github.com/gmatteo/pymatgen