improve basic_usage

[GuiTaek]

I have the following suggestions:

• "or a pipeline containing on of those" to "or a pipeline containing one of those"
• "hyperparameters were fitted in this generation" to "individuals are there in this generation"
• better example (mostly just another algorithm)
• additional explanation that the ranges are (intentionally) bad
• convert snipped code to markable code

every atomic change I did is one commit and every change is reasoned in this commit

the resulting doc: singlehtml.zip