Merge pull request #59 from emilyhsia/treewalk

Type checking and symbol/scope table implemented
fix input = identifier_list bug
fixed issue with 'identifier list' being appended to list conversions
Merge pull request #60 from chrso/master

fixed issue with 'identifier list' being appended to list conversions
Merge branch 'master' of https://github.com/svelTest/svelTest into treewalk
introduce line numbers in Node object so that our tree walker can print line numbers when a semantic error occurs
change type conversions in function_call from identifier_list -> logical_OR_expr
svelTraverse: line numbers in error messages
fix tuple.split(",") bug
check if IDs for params in function_def were already defined in the global scope
throw TypeMismatchError with ID in assignment_expr type checker
change identifier_list rules in yacc : expression -> logical_OR_expr, and add an empty rule(*)

Change so we get the type from logcial_OR_expr returned tuple

(*expression -> empty
logical_OR_expr !-> empty)
update svelTraverse to reflect identifier_list changes in svelYacc
fix bug in getting symbol table entry type when referring to a global symbol
add ID check in lib functions. size() also checks if used the correct number of args (0)
fix assignment_expr not recognizing "array"
remove printed lines in jfunct
remove printed lines in svelTraverse