Add es6 target
Add basic parsing support for let and const
Disallow let and const declarations outside blocks
Fix line endings
Add binder support for block scoped variable declarations
Do not allow use of block-scoped variable before its definition
Ensure duplicate let/const declarations accross files are reported
Report duplicate identifier errors on all locations for merged declarations to align with local declarations
Flag assignments to a const
Flag const declarations shodowed by var redeclarations
Allow const in for statements
Do not allow let and const declarations to be exported from a module
Fix emitting for const in for loops
Switched syntactic classifier to use new tree.

Also added tests.
Merge branch 'master' into letAndConst

Conflicts:
	src/compiler/types.ts
Add language service support for const
Fix search for shadowed const declarations by a var declarations to search for any variable instead of only a blockScoped one to ensure we are not picking it up from a wrong scope.
Respond to code review comments
Allow const and let declarations to be exported in modules. Also ensure that const module elements are not used as references.
Treat blockScoped variable declarations as a separate category when it comes to symbol flags, instead of compining BlockScoped and Variable