Fixed the invalid regex escape

fixes #162

spring-cloud-contract-spec/src/main/groovy/org/springframework/cloud/contract/spec/internal/Headers.groovy

@@ -20,6 +20,8 @@ import groovy.transform.EqualsAndHashCode
 import groovy.transform.ToString
 import groovy.transform.TypeChecked
 
+import java.util.regex.Pattern
+
 /**
  * Represents a set of headers of a request / response or a message
  *
@@ -68,6 +70,10 @@ class Headers {
 		return new DslProperty(value)
 	}
 
+	protected NotToEscapePattern notEscaped(Pattern pattern) {
+		return new NotToEscapePattern(pattern)
+	}
+
 	/**
 	 * Converts the headers into their stub side representations and returns as
 	 * a map of String key => Object value.

spring-cloud-contract-spec/src/main/groovy/org/springframework/cloud/contract/spec/internal/NotToEscapePattern.groovy

@@ -0,0 +1,21 @@
+package org.springframework.cloud.contract.spec.internal
+
+import java.util.regex.Pattern
+
+
+/**
+ * Special case of Patterns that we don't want to escape
+ *
+ * @author Marcin Grzejszczak
+ * @since 1.0.3
+ */
+class NotToEscapePattern extends DslProperty<Pattern> {
+
+	NotToEscapePattern(Pattern clientValue, Pattern serverValue) {
+		super(clientValue, serverValue)
+	}
+
+	NotToEscapePattern(Pattern singleValue) {
+		super(singleValue)
+	}
+}

spring-cloud-contract-spec/src/main/groovy/org/springframework/cloud/contract/spec/internal/Response.groovy

@@ -144,7 +144,7 @@ class Response extends Common {
 
 		@Override
 		DslProperty matching(String value) {
-			return $(p(Pattern.compile("${RegexpUtils.escapeSpecialRegexWithSingleEscape(value)}.*")),
+			return $(p(notEscaped(Pattern.compile("${RegexpUtils.escapeSpecialRegexWithSingleEscape(value)}.*"))),
 					c(value))
 		}
 	}