Merge pull request #3 from galfert/improvements

Some small improvements
Mini refactoring
Add upload-in-progress state
Update jshint config
Add spinner component and use for upload
Introduce nice dialogs
Add sharing function to history
Syntax
Select URL when dialog opens
Update remoteStorage library to 0.8.2-head
Increase remoteStorage timeout to make big uploads work
Ignore case when checking for image extensions