Off by one error in package parsing code leads to template compilation errors

[mvitaly]

Describe the bug
When the temp dir is set to a path that starts with a reserved word (/var/folders/... which is the default on OSX) the template compilation step fails with an exception similar to:

org.fusesource.scalate.CompilerException: Compilation failed:
:2.9 identifier expected but 'var' found.
package var.folders....
        ^
	at app//org.fusesource.scalate.TemplateEngine.compileAndLoad(TemplateEngine.scala:857)
	at app//org.fusesource.scalate.TemplateEngine.compileAndLoadEntry(TemplateEngine.scala:725)
	at app//org.fusesource.scalate.TemplateEngine.liftedTree1$1(TemplateEngine.scala:436)
	at app//org.fusesource.scalate.TemplateEngine.load(TemplateEngine.scala:430)
	at app//org.fusesource.scalate.TemplateEngine.load(TemplateEngine.scala:485)
	at app//org.fusesource.scalate.TemplateEngine.layout(TemplateEngine.scala:582)
...

To Reproduce
Can be reproduced using the following code:

val engine = new TemplateEngine
val source = TemplateSource.fromFile("/var/tmp2/foo.ssp")
source.engine = engine
assertResult("tmp2") { source.packageName }  // will be "var.tmp2" instead

Expected behavior
The compilation of the template should not fail.

Desktop (please complete the following information):

• OS: Mac OSX

This seems to be caused by an off by one error in extractPackageAndClassNames method of TemplateSource trait.
Will submit a PR.