This eliminates the dual solutions and brings Contrib into the
project.json fold.
- Tests are ported to xUnit though SQLite is disabled on DNX due to
Issue #375 (Interop loads fail in the VS runner and  params are busted
regardless).
- Projects are consolidated down to what's currently possible with
project.json.
- Contrib moved to: Dapper.Contrib and Dapper.Tests.Contrib (so tests
appear at the end, no other reason vs. Dapper.Contrib.Tests)
- EF moved to: Dapper.EntityFramework(.StrongName)
- Rainbow moved to: Dapper.Rainbow
- SqlBuilder moved to: Dapper.SqlBuilder
- Packages are removed since it's not current-tooling friendly to keep
them (nor was it using them).
- xUnit implemented in Contrib via abstracts - this allow us to very
quickly add any database provider to the rig in a very concise way.
- Contrib unit tests fixed in various places - they were not
parallel-runner friendly
- Nuspecs removed, since they aren't used anymore (to eliminate
confusion)
- Removed speed tests for libraries that aren't on current versions of
.Net (what would we be comparing?)
- Perf tests moved to Dapper.Tests (consolidation from
Dapper.DNX.Tests), but aren't activated yet (no define)

Fixed missing check for explicit key in Contrib GetaAync()

hacky style - I think we want to remove the program given dnx run exists

This allows full testing from both solutions, all green.

This includes nuget updates for the test libraries but explicitly
excludes the npgsql upgrade, since there are known 2.0 vs. 3.0 driver
issues. If we can assume everyone is able to upgrade - then we should
switch testing over. Alternatively, we need to test both. My preference
would be the former.

This reverts commit 4a70b621.

Disable "Produce outputs on build" from test project; see https://github.com/dotnet/corefx/issues/4578

Update to rc1 (23516 dependencies); implement test skipping (including case-sensntivity check); swap all explicit #if to vague #if so we can iterate without bulk changes

Port tests to xUnit

There's a hit or miss on the dnx run style entry point now - but this
isn't really needed with dnx test, we can just drop the old code IMO.

This let's us run the tests much faster and all from Visual Studio,
command line, and Appveyor.

TODO: Flag missing test methods

Upgrading platform monikers

Update README URLs based on HTTP redirects

Increase extensibility of SqlBuilder.

Fixup NuGet.Config and project.json to get things to compile; core-clr: the gift that keeps on giving

Code cleanup - take 2

- Expression bodies
- Auto-properties (also get-only properties)
- Null propagation
- `nameof` operator
- String interpolation
- Dictionary initializer
- await in finally clause

Add `System.Xml` framework assembly

Without it, Resharper complains about needing the `System.Xml` module when using the `DataTable` class. Project compiles fine without it though. The .NET 4 .csproj file included it as well.

fixed GetAll when used with ExplicitKey