Add tests for the XMLHttpRequest `responseType` property

Closes #260.
Added definition for Event and EventInit
Added tests for the FileList interface
Add CONTRIBUTING.md file which contains CLA.
Modifications to CLA and disclaimer text.
Further modifications to the CLA text.
Update README according to CLA flow changes.
Tests for the Web Notifications spec
remove a stray .gitignore
Add IDL tests for the AudioBuffer interface

Tests generated from the IDL in section 4.9 (The AudioBuffer interface)
of the spec. As we are just testing the interface, the particular
arguments supplied to createBuffer() are inconsequential. We will test
the influence of those arguments in a different test.
Fix issues raised by Simon Pieters
Merge remote-tracking branch 'upstream/master' into submission/ibelem/fileapi-filelist
Fix issues raised by Simon Pieters
Merge pull request #299 from chrislo/submissions/chrislo-audiobuffer-idl-test

Submissions/chrislo audiobuffer idl test
Merge pull request #262 from ibelem/submission/ibelem/fileapi-filelist

Added tests for the FileList interface
Tests for Performance Timeline specifications
Minor editorial change in idlharness test
Merge pull request #300 from plehegar/submissions/performance-timeline

Tests for Performance Timeline specifications
Tests for User Timing
Merge pull request #301 from plehegar/submissions/user-timing

Tests for User Timing