Remove some more cruft for legacy browsers.

https://code.google.com/p/esprima/issues/detail?id=474
Code coverage: ignore known uncovered branches and statements.

https://code.google.com/p/esprima/issues/detail?id=518
Support ES6 MethodDefinition computed keys

https://code.google.com/p/esprima/issues/detail?id=563
Related to #271
Don't insert computed property key into existing properties map

https://code.google.com/p/esprima/issues/detail?id=584
Introduce StringMap to clean up duplicate check code

Introducing StringMap to clean up duplicate check code.
And it fixes some bugs on harmony MethodDefinition's duplication check (__proto__ and key.name lookups).

https://code.google.com/p/esprima/issues/detail?id=585
Follow up the latest ES6 Patterns

https://code.google.com/p/esprima/issues/detail?id=586
computed properties start with a punctuator

https://code.google.com/p/esprima/issues/detail?id=589
Add options.sourceType for disambiguating module parsing mode from script parsing mode

https://code.google.com/p/esprima/issues/detail?id=598
Remove the upper limit of hex digits in Unicode code point escapes

E.g. `'\u{00000000000000000001D306}' == '\u{1D306}'`.

https://code.google.com/p/esprima/issues/detail?id=612
Fix parsing of `import {} from "A";` and `export {};`

https://code.google.com/p/esprima/issues/detail?id=615
Merge remote-tracking branch 'ariya/harmony' into fb-harmony

Conflicts:
	README.md
	esprima.js
	package.json
	test/harmonytest.js
Make tools/generate-test-fixture.js take a --module option for `sourceType="module"` mode

https://code.google.com/p/esprima/issues/detail?id=614
Merge remote-tracking branch 'ariya/harmony' into fb-harmony.jeffmerge
Fix a merge artifact where the computed-ness of generator methods wasnt being represented in the method nodes
Merge pull request #79 from facebook/fb-harmony.jeffmerge

Merge down updates from upstream