Bump Tycho version to 1.5.0-SNAPSHOT

Because:
 - Tycho 1.4.0 does not handle additional repositories in p2.
   I use them to specify that Guava can be automatically
   downloaded from Orbit if the user does not have it installed.

.mvn/extensions.xml

@@ -1,5 +1,5 @@
 <?xml version="1.0"?>
- 
+
 <extensions>
 	<extension>
 		<groupId>org.eclipse.tycho.extras</groupId>

pom.xml

@@ -23,7 +23,7 @@
 
 	<properties>
 		<!-- DEPENDENCIES -->
-		<tycho-version>1.4.0</tycho-version>
+		<tycho-version>1.5.0-SNAPSHOT</tycho-version>
 		<jacoco-version>0.8.1</jacoco-version>
 
 		<!-- SONARQUBE -->
@@ -54,6 +54,13 @@
 		  Also note that it requires my (@echebbi) Bintray credentials.
 	-->
 
+	<pluginRepositories>
+		<pluginRepository>
+			<id>tycho-snapshots</id>
+			<url>https://repo.eclipse.org/content/repositories/tycho-snapshots/</url>
+		</pluginRepository>
+	</pluginRepositories>
+
 	<build>
 		<plugins>
 			<plugin>