Adress minor issues

- rename checkRange() to assertUnitRange()
- use string instead of char

opm/parser/eclipse/EclipseState/Tables/SimpleTable.hpp

@@ -79,7 +79,7 @@ namespace Opm {
         void checkMonotonic(const std::string& columnName,
                              bool isAscending,
                              bool isStrictlyMonotonic = true);
-        void checkRange(const std::string& columnName);
+        void assertUnitRange(const std::string& columnName);
         void applyDefaultsConstant(const std::string& columnName, double value);
         void applyDefaultsLinear(const std::string& columnName);
         void createColumns(const std::vector<std::string> &columnNames);