Bug fix: allow FixedData to be created with a data argument rather than shape+dtype
Allow the creation of time-independent observables
Move creation of box group after checks.
Make arguments to 'observable' explicit.
Add a scalar time independent observable to the example run_h5md
Updates:
1. Allow observables to open properly existing data (TimeData and FixedData).
2. Fix FixedData for opening scalar data.
Add opening of scalar observable to example analyze_h5md.
Merge pull request #8 from khinsen/time-independent-observables

Time-independent observables
Merge branch 'hinsen_pr8'
Add time-dependent box in run_h5md example.