Support EL without jasper by using tomcat-embed-el

Add `tomcat-embed-el` dependency (newly released as part of Tomcat
7.0.52) allowing EL usage without jasper.

Fixes gh-248

spring-boot-dependencies/pom.xml

@@ -176,6 +176,11 @@
 				<artifactId>tomcat-embed-core</artifactId>
 				<version>${tomcat.version}</version>
 			</dependency>
+			<dependency>
+				<groupId>org.apache.tomcat.embed</groupId>
+				<artifactId>tomcat-embed-el</artifactId>
+				<version>${tomcat.version}</version>
+			</dependency>
 			<dependency>
 				<groupId>org.apache.tomcat.embed</groupId>
 				<artifactId>tomcat-embed-logging-juli</artifactId>

spring-boot-starters/spring-boot-starter-tomcat/pom.xml

 <?xml version="1.0" encoding="UTF-8"?>
-<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
 	<modelVersion>4.0.0</modelVersion>
 	<parent>
 		<groupId>org.springframework.boot</groupId>
@@ -16,6 +17,10 @@
 			<groupId>org.apache.tomcat.embed</groupId>
 			<artifactId>tomcat-embed-core</artifactId>
 		</dependency>
+		<dependency>
+			<groupId>org.apache.tomcat.embed</groupId>
+			<artifactId>tomcat-embed-el</artifactId>
+		</dependency>
 		<dependency>
 			<groupId>org.apache.tomcat.embed</groupId>
 			<artifactId>tomcat-embed-logging-juli</artifactId>