Count number of decays that have additional pi0
Add check zero-division when all decays are found
Rename hep_translator() to HepTranslator(object)
Add cleanup if class is used with with

Added a __enter__ and __exit__ function. The latter one deletes the
created files and is called when the object is called with the
'with'-statement.
http://stackoverflow.com/questions/865115/how-do-i-correctly-clean-up-a-python-object
Make import non-relative
add todo functionality to sphinx documentation
Extend Comments and minor fixes
Add more parameters and remove trailing ','
Handle seen as br 0 and dominant as br 1
Add subdecay handling to extract_decay_from_lines

Implement a first version of the subdecay handling, but there is still a
lot todo. Especially:
- more than one subdecay
- br is only "seen", etc
- sub decay mother is named differently than the decay name
File handling works now as intended