Fix typo in documentation
Merge remote-tracking branch 'mpmaster/master'
 Make Task.rmtreee API similaro to the one of WorkFlow.rmtree.
Merge remote-tracking branch 'mpmaster/master'
 Add method dot and norm to core.Lattice to compute norms and scalar products.
Merge remote-tracking branch 'mpmaster/master'
 Add class constructor for AbinitTask
 New methods for Workflow and AbinitTask
 Cleanup abinitio
Merge remote-tracking branch 'mpmaster/master'
 Update doctest (was failing due to the use of the new constant BOHR_IN_ANGS)
 Add polymorphic method Workflow.register to add new tasks.
 Preliminary version of ArrayWithUnit (unit tests are still missing).
Merge remote-tracking branch 'mpmaster/master'

Conflicts:
	pymatgen/core/units.py
 (Almost) final version of ArrayWithUnit
Merge remote-tracking branch 'mpmaster/master'

Conflicts:
	pymatgen/core/tests/test_units.py
	pymatgen/core/units.py
 Add comments in units.py
 Use lazy property for Lattice.reciprocal_lattice  (assume immutable object).