adding redundancy handling to combineFeatures

Changing combineFeatures to enable handing redundancy in feature to grouping factor (e.g. peptide to protein) assignment.
delete unnecessary access through MSnbase::
fixing the previous commit
Merge pull request #18 from vladpetyuk/master

adding redundancy handling to combineFeatures
update desc and news
fixed some errors from previous PR and updated doc
updated testing to testthat 0.8
new dev version
combineFeatures fixes, tests and doc
spacing
more combineFeature cleaning
dummy id data
add utils.leftJoin to replace base::merge
replace merge by utils.leftJoin in utils.mergeSpectraAndIdentificationData and extend test case
Merge branch 'master' into addIdentificationData

Conflicts:
	NEWS
move test_utils.R to new destination: test/testthat/