Improve argument checking, enforce argument naming in Ensure.
Improve test by checking for explicit exception type. Add test for managing syntax edge cases.
Refactor IVariableDeclaration into IVariableBinder, add status#let status directive.
Add the Jefferson.Core/Directives/BlockDirective.cs#blockJefferson.Core/Directives/BlockDirective.cs directive which does nothing but create a block or in otherwords create a new scope.
Improve let parsing and errors and add appropriate tests for status#letstatus and status#blockstatus, more testing will be needed, however.