Replace raw UTF8 parser with String parser (#6)

* Replace UTF8 parser with String based one

* swift format

* Add parsing errors that include context about where error is

* Remove old error tests

Tests/HummingbirdMustacheTests/TemplateParserTests.swift

@@ -31,39 +31,6 @@ final class TemplateParserTests: XCTestCase {
         let template = try HBMustacheTemplate(string: "{{ section }}")
         XCTAssertEqual(template.tokens, [.variable(name: "section")])
     }
-
-    func testSectionEndError() throws {
-        XCTAssertThrowsError(_ = try HBMustacheTemplate(string: "test {{#section}}")) { error in
-            switch error {
-            case HBMustacheTemplate.Error.expectedSectionEnd:
-                break
-            default:
-                XCTFail("\(error)")
-            }
-        }
-    }
-
-    func testSectionCloseNameIncorrectError() throws {
-        XCTAssertThrowsError(_ = try HBMustacheTemplate(string: "test {{#section}}{{/error}}")) { error in
-            switch error {
-            case HBMustacheTemplate.Error.sectionCloseNameIncorrect:
-                break
-            default:
-                XCTFail("\(error)")
-            }
-        }
-    }
-
-    func testUnmatchedNameError() throws {
-        XCTAssertThrowsError(_ = try HBMustacheTemplate(string: "test {{section#}}")) { error in
-            switch error {
-            case HBMustacheTemplate.Error.unfinishedName:
-                break
-            default:
-                XCTFail("\(error)")
-            }
-        }
-    }
 }
 
 extension HBMustacheTemplate: Equatable {