Add mkdocs site to ignore list
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Initial version of the project documentation.

1. The docs are divided into 2 sections: User guide which covers getting
started, current NLP tasks (outline only) and samples (POS Tagger from doc
dir).
2. The About section covers technical notes, license and support information.
3. The initial index file is derived from the README.md in the root dir.
4. Finally MkDocs configuration for the doc site.
Merge pull request #23 from dmsurti/add-docs

Add RTD documentation