Properly report errors for failed type assertions
Merge pull request #618 from Microsoft/typeAssertionErrors

Properly report errors for failed type assertions
Corrected codegen to support shadowed module names.
Fixing a few issues in Language Specification
Merge pull request #624 from Microsoft/updateLangSpec

Fixing a few issues in Language Specification
Merge pull request #623 from Microsoft/shadowedModuleNames

Corrected codegen to support shadowed module names.
Corrected some spelling/grammar issues.
Updating Language Specification
Merge pull request #626 from Microsoft/typoscript

Corrected some spelling/grammar issues.
Merge pull request #627 from Microsoft/updateLangSpec

Updating Language Specification
Merge branch 'master' into specConformanceTests