Fix issue #63. Code cleanup.
prevent data.full() in __str__ if the system is huge to prevent memory error (ipython always evaluates all representations even if it isnt used, so it can cause a memory error in a notebook even though _repr_latex_ is the one that is finally displayed)
bra and ket working ad documented
more qubit conventions, spellchecking and note on qstate
small line-breaking
pep8ization plus some docstring polish
Added checks for parameter values. Closes #66.
Merge pull request #65 from stared/braket-sugar

Braket sugar