Add a suitable .gitignore for build files
Improve error handling for misconfiguration

Avoid a NullPointerException when no apiSources have been configured. Also
reorder the exceptions so the GenerateException is not swallowed, and convert
the generic exception handling to a MojoExecutionException so that the trace
is shown.
Maven 3.1.0 compatibility

Remove the call to the converter that is not needed
(http://s.apache.org/maven-class-realm-converter) to avoid failing on Maven
3.1.0. The API will be restored in Maven 3.1.1, but this should work in
either case.
Merge pull request #15 from brettporter/maven-3.1.0-compat

Maven 3.1.0 compat