* Translation: Update binary_tree.md
simplified some parts while others added a few words to make it clearer
* translation: Update binary_tree.md
edited most of the stuff that QiLOL has suggestion, again thanks QiLOL for the review
* translation: Update binary_tree.md
changed to simpler words instead.
Did not update the 2nd part, as I'm waiting for Khrahets to make the final decision
* Translation: Update index.md
simplified the words using "vibrant" instead. used illustrate instead of demonstrate because I'm thinking the image "illustrates" the concept.
* Translation: Update index.md
Changed to what yuelinxin has suggested. thanks for the suggestion.