Remove tags instead of replacing with spaces.

See:
https://github.com/dae/anki/commit/3326254eec2ac80eea2fc3d4b4552963db4832ed

fix cloze+latex issue in media check, and duplicate answers (#757, #758)

We were replacing spans with spaces during review but not during media check.
just strip the tags instead, which makes the media check consistent and
doesn't result in multiple identical answers.
Replace &nbsp; with spaces within stripHTML.

See:
https://github.com/dae/anki/commit/2ba8c41fec6f8abf86efdab3ae985e967f0a8bc6

replace nbsp with standard space when stripping html

fixes https://anki.tenderapp.com/discussions/ankidesktop/1952-duplicate-not-detected-on-paste
Do not remove tags as stripHMTL already does that.

See:
https://github.com/dae/anki/commit/988fc102d803f4c8b6d52640536f6a24d3bc696d

remove redundant regex in latex code
Merge pull request #83 from flerda/v2.1-latex

Updates to LaTeX code.