fix some errors and rewrite sentences in README.md (#133)
* Update README.md
line 23, 24 and 25: Remove "that" because "that" is unnecessary in these three sentences.
line 33: Rewrite this sentence and make it more straightforward.
line 34: This first sentence is incomplete.
line 117: “focusses" -> "focuses"
line 118: "continuous" -> "continuous"
line 119: "consise" -> "concise"
* Update README.md
