updated README for consistency

The documentation section has all sentences ending with a period except for number 3. I've added the period to make the section more consistent with the rest of the document.
disabled scroll focus for readonly elements
fix(ionOptionButton): vertically align content

Closes #2348
fix(scrolling): fix overflow scrolling when side menu and main content both use overflow scrolling. Closes 2201
fix(popup): hide buttons div if there's no buttons to show. Fixes #2344
fix(tap): prevent possible click error in specifc android devices. Fixes #2235
update doc for on function

The on function can take a 4th parameter : options
fix(scroll): calling ionic scroll methods blur any selected input elements. Closes #2244
Merge pull request #2440 from MyBoon/patch-1

docs(): update doc for gesture 'on' function
Merge pull request #2383 from AleksMeshkov/master

fix(keyboard): disabled scroll/focus for readonly elements
fix(pullToRefresh): fix animated icon sometimes not showing
test(pullToRefresh): fix test broken in PR
feat(fonts): platform specific fonts
Prevent 'cannot read' exception

On Android (4.4.4) I'm getting "Cannot read property 'options' of null" each time, 100% reproducible.
This small check will not hurt anyone but will prevent unhandled exception error.
docs(ion-tab): fix typo in badge css class example

Closes [#214](https://github.com/driftyco/ionic-site/issues/214)
refactor(ionSlideBox): use live nodeList to preserve ordering
chore(): remove unused platform css
chore(): cleanup unused variables
refactor(scrollBar): rAF scrollbar transitions

Only make changes to the scrollbar element’s style when there is a
change, and use requestAnimationFrame when there is a change.
refactor(clickBlock): transform css for click block

Use transform/opacity CSS properties to show and hide the click block
element, and use requestAnimationFrame for the DOM changes. This is
easier for the GPU to use transform/opacity properties instead of the
display property, and also reduces any potential reflows.