Fix for unparseable date

See occurred exception: 
```
[ERROR] Failed to execute goal net.oneandone.maven.plugins:prerelease:1.6.3:locksmith (default-cli) on project standalone-pom: Execution default-cli of goal net.oneandone.maven.plugins:prerelease:1.6.3:locksmith failed: invalid date in line 1 Tue Aug 26 17:21:53 2014: Unparseable date: "Tue Aug 26 17:21:53 2014" -> [Help 1]
org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal net.oneandone.maven.plugins:prerelease:1.6.3:locksmith (default-cli) on project standalone-pom: Execution default-cli of goal net.oneandone.maven.plugins:prerelease:1.6.3:locksmith failed: invalid date in line 1 Tue Aug 26 17:21:53 2014
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:224)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
	at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:116)
	at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:80)
	at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build(SingleThreadedBuilder.java:51)
	at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:120)
	at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:347)
	at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:154)
	at org.apache.maven.cli.MavenCli.execute(MavenCli.java:584)
	at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:213)
	at org.apache.maven.cli.MavenCli.main(MavenCli.java:157)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:483)
	at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:289)
	at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:229)
	at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:415)
	at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:356)
Caused by: org.apache.maven.plugin.PluginExecutionException: Execution default-cli of goal net.oneandone.maven.plugins:prerelease:1.6.3:locksmith failed: invalid date in line 1 Tue Aug 26 17:21:53 2014
	at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:143)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:208)
	... 19 more
Caused by: java.lang.IllegalStateException: invalid date in line 1 Tue Aug 26 17:21:53 2014
	at net.oneandone.maven.plugins.prerelease.Locksmith.startedMap(Locksmith.java:153)
	at net.oneandone.maven.plugins.prerelease.Locksmith.doExecute(Locksmith.java:69)
	at net.oneandone.maven.plugins.prerelease.Base.execute(Base.java:89)
	at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:132)
	... 20 more
Caused by: java.text.ParseException: Unparseable date: "Tue Aug 26 17:21:53 2014"
	at java.text.DateFormat.parse(DateFormat.java:366)
	at net.oneandone.maven.plugins.prerelease.Locksmith.startedMap(Locksmith.java:148)
	... 23 more
```