4-cola implementation
Added insert6 and -rts-opts --with-rtsopts=-N
-fspec-constr is implied
flailing around trying different configuration options
Merge branch 'master' of github.com:ekmett/structures into 4-cola

Conflicts:
	benchmarks/inserts.hs
	src/Data/Vector/Map.hs
	structures.cabal
Merge branch 'master' into 4-cola
switch to a full four way merge with no luck
Merge branch 'master' into 4-cola

Conflicts:
	src/Data/Vector/Map.hs
Removed Hashable constraints
benchmark cleanup
match file name to benchmark name