YaOzI

This PR changes: - and/or -> `and`/`or` - &/| -> `&`/`|`

This PR fix the following typo: `tesselation` -> `tessellation`

[4.1 Introduction]: why `add_python` is faster than `add_numpy` for vectorization `add`

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I found an opposite conclusion when running the example code in **4.1 Introduction**, following code is my results tested in IPython 6.4.0 with Python 3.6.5 and Numpy 1.14.3: ```python In...

Append two lines: `log/` `build/` to the `.gitignore` file.

Fix the erroneous `.gitattributes` file.