Update README.md

Added a "Getting Started" section to the documentation.
Update README.md

Changed to better practices.
Manually create dash.webm.all.js for DASH with WebM

This patch creates dash.webm.all.js and dash.webm.min.js using the
Gruntfile in contrib/webmjs. This can be used by those who need
WebM support in their dash player without having to go through the
process of setting up and building this file using node and grunt.
Fix WebM SegmentInfo parsing bug

Existing WebM SegmentInfo parsing is strict and expects elements in
a specific order (which is against the matroska specification [1]).
This patch relaxes parsing of SegmentInfo and allows valid files
to be played back properly.

[1] http://matroska.org/technical/specs/index.html
Manually update dash.webm.*.js

Update WebM Dash js files by running grunt.
fixes a reference to MetricsExtensions in MediaPlyaer.getDVRInfoMetric function
fixes file references for videojs example page
fixes file references for webmjs example page