Fixed the last linting errors.

src/app/converter/base64encoder.ts

@@ -14,7 +14,9 @@ export class Base64Encoder implements Converter {
       return btoa(input);
     } catch (exception) {
       console.error(exception);
-      throw new Error('Ouch! Looks like you've got a UTF-8 character there. Too bad, this is not supported yet. We're working on it and hope to be ready soon! Why don't you <a href=\'https://duckduckgo.com/?q=cute+kitties&iar=images\'>enjoy some kittens</a> meanwhile?');
+      throw new Error('Ouch! Looks like you\'ve got a UTF-8 character there. Too bad, this is not supported yet. '
+        + 'We\'re working on it and hope to be ready soon! Why don\'t you '
+        + '<a href="https://duckduckgo.com/?q=cute+kitties&iar=images">enjoy some kittens</a> meanwhile?');
     }
   }
 }

src/app/converter/bintodecconverter.ts

@@ -10,7 +10,7 @@ export class BinToDecConverter implements Converter {
   }
 
   convert(input: string): string {
-    let n: number = parseInt(input, 2);
+    const n: number = parseInt(input, 2);
     if (isNaN(n)) {
       throw new Error('The input seems not to be a valid binary number.');
     }

src/app/converter/dectobinconverter.ts

@@ -10,7 +10,7 @@ export class DecToBinConverter implements Converter {
   }
 
   convert(input: string): string {
-    let n: number = parseInt(input, 10);
+    const n: number = parseInt(input, 10);
     if (isNaN(n)) {
       throw new Error('The input seems not to be a valid integer.');
     }

src/app/converter/dectohexconverter.ts

@@ -10,7 +10,7 @@ export class DecToHexConverter implements Converter {
   }
 
   convert(input: string): string {
-    let n: number = parseInt(input, 10);
+    const n: number = parseInt(input, 10);
     if (isNaN(n)) {
       throw new Error('The input seems not to be a valid integer.');
     }

src/app/converter/hextodecconverter.ts

@@ -10,9 +10,9 @@ export class HexToDecConverter implements Converter {
   }
 
   convert(input: string): string {
-    let n: number = parseInt(input, 16);
+    const n: number = parseInt(input, 16);
     if (isNaN(n)) {
-      throw new Error('The input seems not to be a valid hexadecimal number.')
+      throw new Error('The input seems not to be a valid hexadecimal number.');
     }
     return n.toString(10);
   }