- reformat README.md
  - merge 'Git tag' and 'Git branch' columns
  - remove old v3.2.4 / v5.2.4 information
  - add v3.2.7 / v5.2.7 information

- test using netcoreapp2.1
- react to .NET Core breaking change
  - see https://docs.microsoft.com/en-us/dotnet/core/compatibility/2.1#path-apis-dont-throw-an-exception-for-invalid-characters
- suppress NU5125 warnings
  - break the build because warnings are treated as errors
- do not validate Expires header values
  - aspnet#263

Constrain the MemoryStream size

Fixes aspnet#310

aspnet#312)

* Configure max request line size limits to be the same as maxHeaderSize

As part of ReadAsHttpRequestMessageAsync, the parsing of the HTTP request line is limited
by a non-configurable 2k limit. The size does not affect buffer sizes, only the maximum allowed length.

This PR updates the ReadAsHttpRequestMessageAsync API to use the same limits for HTTP request line
as the HTTP header line, the latter which is configurable by user code.
In the default case, this means the HTTP request line size now supports a 16k limit before it throws.

Fixes aspnet#307

- remove `<requireLicenseAcceptance/>` as well
  - can't require a license w/o `<license/>` or `<licenseUrl/>`
- also, don't need to ignore NU5125 anymore

- brings in recent fixes from last release