Fix doctests in comments2rst.py

Added optional tags and fixed a couple spacing/newline things.
Small "doctest" fix

worksheet2rst.py
fix doctests in sagenb/notebook/cell.py
fix doctests in sagenb/notebook/notebook.py
fix KeyError in user_manager.py
fix doctest in user_manager.py
fix doctests in sagenb/notebook/worksheet.py
Merge pull request #160 from kcrisman/sws2rst

Sws2rst updates - fix doctests.
add nodoctest.py to directories that should not be doctested
replace tmp_dir+'.sagenb' with tmp_dir(ext='.sagenb')
Merge pull request #161 from ppurka/doctests

Fix doctests in sagenb directory