Update bootstrap-rtl v3.1.1 (critical bug fixes)

This is a critical bug fix to a previous version, and removal of invalid version (3.1.2).

Note: `npm test` passed, and `package.json` updated.

Thanks,
Morteza

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Downloaded from: https://github.com/ratnic/bootstrap-rtl/releases/download/v3.1.1/bootstrap-rtl-v3.1.1.zip

Homepage: https://github.com/ratnic/bootstrap-rtl
Popularity: Has 131 stars, around 1000 daily visitors, and the most popular project in countries with right to left scripts e.g. Farsi, Arabic, and Hebrew (According to the BitDeli).