Removing trailing white spaces and fixing typo

[Bojun-Seo]

Trailing whitespaces are removed from all files, empty lines and image files are preserved. This patch is created using the following shell commands:

find . -type f -not -path '*/\.*' -exec sed -i '/^$/!s/[ \t]*$//' {} \;

fixing typo
Before: its possible to ~
After: it's possible to ~

[chenhengqi]

I personally don't like this kind of whitespace changes(for non first-time contributor). Please invest your efforts on something more meaningful.

[yonghong-song]

Okay. I will merge this since it does makes format (esp. at 'git' level) better across the repo. Hopefully in the future, we do not have such format issues.

Agree with @chenhengqi that actually fixing the issue and had new features will be much better.