Fix build

[zyzhu]

I've made some attempts to fix the build on machine with only VS2017 and R-3.4.3 installed. I've also fixed the travis build (It's my first time trying travis. I followed similar travis settings from ProjectScaffold and FSharp.Data). All tests are passed on travis now.

• Updated FSharp.Core to 4.2.3 (aligned with fsharp.formatting) and referenced nuget source instead of the one on machine. Target FSharp 4.4.1.0 now. I didn't attempt to go all the way to dotnet standard yet as I'm not sure whether RProvider will work or not.

Updated the following build tool chains.

• FSharp.Formatting 3.0.0-beta11 (lots of breaking changes from FSharp.Formatting 2.x. Fixing this took most of time. But the documents generated locally look alright)
• FSharp.Compiler.Service 22.0.3 (old compiler services had bug and documents cannot be generated on mono)
• FSharp.Data 2.4.6
• Math.Numerics 4.5.1
• RProvider to 1.1.20
• NUnit 3.8.0
• FAKE 4.64.13

One thing that I'm not sure is I commented out the fsi files in Deedle project. I couldn't compile the library with them included. But all tests are passed. Please let me know what these files are for. @tpetricek FSharp.Data\TextRuntime.fsi FSharp.Data\StructuralTypes.fsi FSharp.Data\StructuralInference.fsi FSharp.Data\CsvRuntime.fsi FSharp.Data\CsvFile.fsi FSharp.Data\CsvInference.fsi

[tpetricek]

I'll merge this now, but I opened issue #387 because I think this PR disabled documentation test - which is not crucial but would be nice to fix at some point.

[tpetricek]

Doh, it turns out that I still only have VS2015 on my machine and this does not build with VS2015. I guess I'll have to update before doing more work on this :(

[zyzhu]

@tpetricek I’ve fixed the build with the latest commit. Tested on Vm with only VS2015 and R3.4.3.