Added Support For Nested Mappings

[ayushya]

This is an additional Feature, to support the relative paths generated after compiling scss through 'compass'.

This PR adds the opt-in feature which adds the nested mapping of the assets.

As of now, all the links to asset files which are mapped are searched in all the files to be busted[replace the old link to assets to new mapped hashed links]

For E.g.

<img src="assets/images/homepage/myProfile.img">

Will be mapped with

<img src="assets/images/homepage/myProfile.ah21as.img"> 

But for the case when we are dealing with relative paths, the links wouldn't be replaced.

For E.g.

<img src="../images/homepage/myProfile.img">

For the above case, there would be no change in the file as it could not find
"assets/images/homepage/myProfile.img" to be replaced by "assets/images/homepage/myProfile.ah21as.img"

To support the feature all we need is add the following option in gruntfile:

            nestedMappings: true,
            nestedMappingsPattern: [
                {
                    pattern: 'assets/images/',
                    splitAt: 'assets/'
                }
            ]

I have also updated the Readme file for instructions to use it.

[benhoIIand]

Hi @ayushya. I understand that this is a use case that could potentially crop up a few times, but my advice would be to not use relative paths for static assets - is there a reason for you using them over absolute paths from the root?

I'd always use this
<img src="/assets/images/homepage/myProfile.img">

over this
<img src="../images/homepage/myProfile.img">

[glhewett]

Hi @hollandben, I used to think that we should always use absolute paths since I spent many years in a rails environment, but over the years I have see more and more single page apps support relative paths to assets to that the app can be deployed into any path. Specifically, one app that I work on has the ability to deploy to gh-pages on the forked repo so that new changes can be shared with the team easily. Would you consider merging this PR if updated and meets all of our other contribution requirements?

[glhewett]

Or merge a different PR that solves the same issue?

[richardhinkamp]

#211 fixes the relative path issue too, different approach so it works for all relative paths without any config.

[glhewett]

Cool, I made that comment before your PR. Thanks for that!