Make `.lb-nav` element cached
Refactor image loading

Add possibility to add more album entry types.

Create separate classes AlbumEntryFactory and Img represented an image entry.
Use `load` function to have possibility to have own loader function for each
album entry types.

Move "fit image" related code to a separate function `_fitImage`.
Add classes to previews and container depending on the album entry type
Add experimental support for Youtube embedded videos

Also add a sample style for "youtube" images.
Merge branch 'dev-youtube' into dev
Merge branch 'dev'
README: Add information about v1.0.0
Update header comment
Add build stuff
Grunt: Add a task which updates version in lightbox-phts.js file's comment
Merge branch 'master' into dev
Fix missing semicolons

Found after jshint.
Fix comment to be ignored by uglifier