ResourceInjector was not respecting custom bootstrap css files. Fixed by
removing <stylesheet>s and adding injectCss calls to configure().

Custom css files can live anywhere now, including in a Maven
src/main/resources tree (instead of the src/main/java tree).
Updated Configurator documentation to illustrate.
Merge pull request #467 from gregsheremeta/master

ResourceInjector was not respecting custom bootstrap css files. Fixed by