Fixed some typos of chapter 1 + updated .gitignore file

Hadamard operator that was mentioned in first paragraph of section 1.2.4, was not defined before.
As a matter of fact in example 1.2.2 you defined this operator (eq. 1-1) but you didn't put a name on it.
You can fix this by mentioning the name of this operator here in example 1.2.2.