Create lazy row reader for virtual vectors, split VirtualFrame implementation
Support merging on virtual data frames and series
Merge branch 'tpetricek.PerfTests'
Fix tests (recent optimization)
Merge branch 'master' of github.com:BlueMountainCapital/Deedle
Update RProvider reference and Require specific versions
Make build compatible with cygwin/git shell
Update F# Data and RProvider dependencies

This updates the references to the latest version and also changes the NuGet
dependency to require a specific version (which is required by the load scripts
and also to make the FsLab NuGet package work)
Merge pull request #266 from tpetricek/master

Adding support for merging on virtual frames