Testing `data-width` attribute.
Fixing `data-width` implementation.

`data-width` should be copied only if set.
`hasAttribute` -> `getAttribute` to fix IE8 issue.
Removing defaults IE `gif.width`/`gif.height` atrributes.
More relevant tests for `determineAppropriateResolution`

- definitely sorting out the relationship with image size and `data-width`
- expanding image based on container's size
Fixed interpolation.
`{width}` calculation is now performed against parent size.
Taking in account `data-width` as stated in the README.

Thanks Past Me for documenting it!
Merge pull request #83 from BBC-News/fix-83

Image width is set as 0 sometimes
Merge pull request #86 from BBC-News/fix-86

Containers above max image size load smallest image
Option to stop redundant download of small images.

This option stops Imager.js downloading a new image when a higher
resolution copy has already been downloaded. This can occur when a
mobile device is rotated from landscape to portrait.

Upscaling to larger images is unchanged.
Make default behaviour following discussion at #77

And fixes 'strict' warning for getNaturalWidth definition.
Fix jshint complaints #77
Porting `determineAppropriateResolution` to a dedicated section.

- splitting the test case for more granularity and TDD conformance
Moved the `availableWidths` to `html-options`.

- it is where the other existing alternatives are tested
- this is where the natural width test is going to be written
Forwarding `data-width` and adjusting responsive image size.
Updated CHANGELOG
Updated CHANGELOG
Updated CHANGELOG
Preparing 0.3.0-beta.1