Address issue #195 with my recent Deque port from C# Codeplex implementation
Use our own Deque - references #195
Merge remote-tracking branch 'victor/mainline' into Deque

Conflicts:
	src/Deedle/Stats.fs
Simplified the Deque since we are not using everything
Use more idiomatic let bindings
Cleanup
Use more idiomatic let bindings
Cleanup
Fixing bugs in original Deque implementation
Use and test Deque indexer
Add test for uncovered path in Deque
Merge pull request #202 from tpetricek/GH201

Add more options for the Lookup operation (#201)
Merge remote-tracking branch 'main/mainline' into mainline
Merge new Deque implementation, recover tests
Merge new deque implementation and some speedup

The new Deque is slightly slower (say 10%), but there was enough room for
other optimizations elsewhere, so I made a couple of minor tweaks in Stats
module and so the overall result is now faster. Not sure what is different
in our F# queue - it is likely just my use of Debug build.