Fix mistakes or add clarification in tutorial

[amitaibu]

Some great suggestions from @dokumori:

Page URL: http://shoov.io/tutorials/lesson1-install/

Problem: Installation of shoov-webdrivercss failed on OSX 10.11.1 even with 'sudo'. The component had to be installed separately by running 'sudo npm install --save shoov-webdrivercss'

Problem: the tutorial assumes that one has nodejs installed on her/his machine already.
Suggestion: Add a brief description that nodejs is required: https://nodejs.org/en/download/

Problem: The following description is unclear

'5. Get the ~/.shoov.json file by following the copy/ pasting the code in your terminal. This file holds your Shoov access token, and the BrowserStack credentials which will be automatically picked up when doing visual monitoring'

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Page URL: http://shoov.io/tutorials/lesson3-static-page/

Problem: at the top it says "we just need to adapt the following piece of code", but it is not clear where the code is stored.
Suggestion: make the filepath explicit in the documentation

Problem: The code shown on the page is not identical to what is in the directory

Example on the website: it('should show the static page',function(done) {

The actual code: it('should show the home page',function(done) {

Suggestion: update the code on the page

[ordavidil]

@amitaibu
There is also a broken link on http://shoov.io/tutorials/lesson3-static-page/

[amitaibu]

@ordavidil can you create a PR please for the broken link.

[ordavidil]

Sure