Adding a dapper specific feed, for much easier pushing to NuGet. When
they implement Ctrl+Click in the UI this won't be necessary...or we
break down and automate it finally. Depends on signing plans later.

Removes NuGet workaround for pre-2.0 and lines up with other script
enhancements since.

Micro optimizations for CreateParamInfoGenerator

AddDynamicParameters repeated should work  while paramtype is DbString 

Netstandard2.0 Followup Cleanup

.NET Standard 2.0, for great justice.

This change:
- Removes the Assert shim
- Uses recommended xUnit methods (improving fail errors)
- Cleans up exception tests
- General test formatting fixes
- Removes the netcoerapp1.0 only testing (oops commit)

New overload so this isn't a breaking change. We can collapse down in v2.0 (including the Impl method).

Add dynamic overloads for:
- QueryFirstAsync
- QueryFirstOrDefaultAsync
- QuerySingleAsync
- QuerySingleOrDefaultAsync

This may change a lot in 2.x, but many people asking for them now so here they are. Unit tests also fixed for QuerySingleOrDefaultAsync.

Note: this builds on the netstandard2 branch because of the xUnit changes to go with VS 2017 15.3.

.NET Core 2 SDK is on the base Appveyor image now

This uses the new non-parallel-at-the-end I added to xUnit in https://github.com/xunit/xunit/pull/1411 This way we can run any global test that are other-test-unfriendly much more easily.

* Enable SqlDataRecord TVPs on netstandard1.3.
* Update netstandard2.0 SqlClient references to Preview 2.
* Skip TransactionScope tests for netcoreapp2.0.
- According to https://github.com/dotnet/corefx/issues/12534, ambient transaction enlistment is not included with .net core 2.0.
* Update references in Dapper.StrongName.
* Disable parallel test run to stabilize flaky type handler tests.
* Disable parallel test run by assembly attribute.
* Move Issue461 tests to TypeHandlerTests.
* Group type handler tests in a collection, re-enable parallelization.
- Being part of the same collection, type handler tests will run sequentially. All other tests can run in parallel.
* Move tests relying on query cache & type maps to a separate collection.

This reverts commit e7ad0874.

Markdown tables instead of html
“Can be faster” in correct row

OperationsPerInvoke is an informational, not instructional property.
What we actually want is the UnrollFactor. Moved into the job definition
to simplify things.

* Fix for PostgresAdapter in SqlMapperExtensions.Async. Copied same line of code from SqlMapperExtensions to fix RuntimeBinderException on InsertAsync
* Cleanup

Use an HTTPS link where possible.
Fix 404 for performance tests.