allow only jpg/png for filepicker
improve IA of some pages

* pages are proofs#new, proofs#edit, requirements#index, and
* copy was improved for home#index and comments added

* dashed_name method added to convert requirement names containing dots
to dashes.
Merge pull request #112 from akshatpradhan/ux_redesign

improve IA of some pages
fix rendering bugs in safari for a better UX
* Add `pulse` and `pulse-container` CSS classes for better icon pulse on home page
* Apply the `pulse` class to elements you wish to use the pulse animation on and `pulse-container` on the ancestor element which will trigger the pulse when the user hovers over it
* fix text issues on Safari during hover CSS animation using GPU http://stackoverflow.com/questions/7947385/hovering-over-css-transition-in-safari-lightens-certain-font-color
Rename CSS file
Merge pull request #113 from akshatpradhan/sguha

fix rendering bugs in safari for a better UX
Merge pull request #116 from akshatpradhan/fix106

user expects be restricted to uploading png and jpg only
user expects to see evidence history date
Merge pull request #118 from akshatpradhan/revision_history

user expects to see evidence history date
update screenshot for marketing page
Merge remote-tracking branch 'origin/master'