preview tab redesign (WIP)
Merge branch 'master' into preview_tab_design

# By Dimitry Solovyov
# Via Dimitry Solovyov (1) and Roman Pominov (1)
* master:
  Stricter styles for widget buttons
preview tab i18n
preview tab some css
fix file size in preview tab
different error messages in preview tab
update texts on preview tab
`reject('image')` in `File`
dialog preview uploading state design
Merge pull request #37 from uploadcare/preview_tab_design

Preview tab design