Updated language grammar for project2
Replaced char type with string type
Modified the test cases to fit project2 grammar changes
Removed all charExpr and replaced them with stringExpr
Replaced CST data type with Tree data type
Fixed issues Alan pointed out
Now updating id types in the symbol table during parse
Changed _SymbolTable to _SymbolTableList for multiple scopes
Updated symbol table display to display multiple tables (scopes)
Added ast.js and created global var _AST
No longer modifying source code in lex

No longer modifying source code when the user forgets the EOF token or
places text after the EOF token
Fixed the off by 1 issue when displaying the symbol table(s)
Introduced scope to parser.js and improved symbol table construction
Parser now recognized undeclared and redeclared variables
Parser now recognizes unused variables
Fixing _SymbolTableList off by 1 index issue in parser.js now
Updated test cases
Merge branch 'Project2'