Warn about usage of non-breaking space

[byara]

Reference issue: #85

What changed in this PR:

This PR adds a warning about usage of non-breaking space in a template. Regarding this issue, a unit test is added.

[byara]

This issue could be addressed also by creating a new Token for non-breaking space and Melody would automatically throw a warning like, Invalid Token Expected symbol but found NonBreakingSpace instead.

[pago]

Question: Do we also want to cover other unicode sequences which represent whitespace?

Resources:
https://codepen.io/rubikzube/pen/wolgB
http://xahlee.info/js/js_whitespace.html
https://mathiasbynens.be/notes/javascript-escapes
https://mathiasbynens.be/notes/javascript-unicode

[byara]

Question: Do we also want to cover other unicode sequences which represent whitespace?

Resources:
https://codepen.io/rubikzube/pen/wolgB
http://xahlee.info/js/js_whitespace.html
https://mathiasbynens.be/notes/javascript-escapes
https://mathiasbynens.be/notes/javascript-unicode

I believe it is a good idea to address all unicode sequences which represent whitespace. It prevent the future bugs/bug reports regarding these type of issues.

We can also follow Babel example and use something similar to https://github.com/xtuc/charcodes/tree/master/packages/charcodes and use charCodeAt. Or just add the characters and address them in the appropriate function. One benefit of using charCodeAt + the separate package would be to target characters that cannot be easily read or shown.

[pago]

Do what you think is best. :)

[pago]

As discussed we will want to protect from some additional characters or at least use a unicode representation within the code to avoid confusion.