bump Scala version to 2.10.3
Remove redundancy in excludeFilter default implementation.
'makePom' should not generate <type> elements for standard classifiers.  Fixes #728.

The <type> element was generated for any explicit Artifact with a type other than "jar".
withSources() and withJavadoc() create explicit Artifacts of this kind, but shouldn't
have <type> elements.  They are primarily artifacts with classifiers- the type is an
Ivy aspect.  So, when writing to a pom, don't use write a type for known classifiers.