doc: mention WriteHeapDump in 1.3 release notes

https://code.google.com/p/go/source/browse/doc/go1.3.html?r=603f6c3b152cba501098d410b21b4ebad730a52b

refs #44
doc: add release note for 'godoc -analysis'

refs #44
Merge pull request #59 from gophersjp/issue/44

doc: go1.3.html Issue/44