Fixed  `start_url` processing issues (closes #201)

* added document URL as arg to the algorithm.
* If the URL is the empty string or undefined, then it should return
the URL of the top-level browsing context.
* If the URL is in error, it should return the URL of the top-level
browsing context.
Merge pull request #202 from w3c/process_start_url

Fixed  `start_url` processing issues (closes #201)
Rewrite of fetching and processing (closes #17, #186, #188, #195, #198 )

* Formalizes using link element as the solution (closes #17)
* Banned media attribute. At least, we say that it's not considered
during processing. (closes #186)
* Added text about when events need to be fired (closes #188)
* The fetch part of the specification now mentions the crossorigin
attribute (closes #195)
* fixed copy/pasta error relating to icons/orientation (closes #198)
* fixed a whole bunch of editorial issues.
Fixes based on @kenchris's feedback

* various fixes suggest by @kenchris
* moved icon and name fallback behaviour out of processing section.
Merge pull request #203 from w3c/cors

Rewrite of fetching and processing (closes #17, #186, #188, #195, #198)
Killed events as @mounirlamouri suggested (closes #188)
Merge pull request #204 from w3c/kill_events

Killed events as @mounirlamouri suggested (closes #188)
Added context to request (closes #205)
Merge pull request #206 from w3c/manifest_context

Added context to request (closes #205)
fixed small markup issues
Added links to implementation status
fixed small markup issues
fixed typo
Minor editorial nits

Minor editorial nits; ignore if you'd like @marcosc ;-)
Minor editorial nits

Fix a typo for the URL spec reference and for consistency, remove "Note:" prefix for paragraphs with class=note
Minor editorial update

Add a missing class=note to one of the notes.
Editorial nits

Fix a ref to [URL] and for consistency, wrap arguments with <code></code>
Update index.html

Editorial
Merge pull request #213 from wwumit/patch-1

Update index.html
Fixed link to blink imp. bug (closes #216)