a number of changes

DESCRIPTION: Move Rcpp (>= 0.11.0) from Depends: to Imports:
NAMESPACE: Added importFrom(Rcpp, evalCpp)
.Rbuildignore: Added .travis.yml and doxyfile
src/RInside.cpp: Added --vanilla --slave to default arguments
src/Makefile: PKG_LIBS no longer points to Rcpp's library
inst/examples/standard/Makefile: Note that Rcpp (>= 0.11.0) no longer
requires the RCPPLIBS variable
inst/examples/standard/rinside_test0.cpp: Minor tweaks
inst/examples/standard/rinside_sample9.cpp: In this already-disabled example,
comment out a data structure no longer provided by Rcpp