Prepare for 1.7.0 release (#353)

* Prepare for 1.7.0 release

* minor

Merge pull request #283 from guzzle/null-header-value

Accept null and bool header values again

fix changelog title levels

Release 1.5.2

Release 1.5.1

Release 1.5.0

* Reverted BC break to `Uri::resolve` and `Uri::removeDotSegments` by…

… removing

  calls to `trigger_error` when deprecated methods are invoked.

* Reverted BC break by reintroducing behavior to automagically fix a …

…URI with a relative path and an authority by adding a leading slash to the path. It's only deprecated now.

* Added triggering of silenced deprecation warnings.

* Fix `Stream::read` when length parameter <= 0.

* `copy_to_stream` reads bytes in chunks instead of `maxLen` into memory.
* Fix `ServerRequest::getUriFromGlobals` when `Host` header contains port.
* Ensure `ServerRequest::getUriFromGlobals` returns a URI in absolute form.
* Allow `parse_response` to parse a response without delimiting space and reason.
* Ensure each URI modification results in a valid URI according to PSR-7 discussions.
  Invalid modifications will throw an exception instead of returning a wrong URI or
  doing some magic.
  - `(new Uri)->withPath('foo')->withHost('example.com')` will throw an exception
    because the path of a URI with an authority must start with a slash "/" or be empty
  - `(new Uri())->withScheme('http')` will return `'http://localhost'`
* Fix compatibility of URIs with `file` scheme and empty host.
* Added common URI utility methods based on RFC 3986 (see documentation in the readme):
  - `Uri::isDefaultPort`
  - `Uri::isAbsolute`
  - `Uri::isNetworkPathReference`
  - `Uri::isAbsolutePathReference`
  - `Uri::isRelativePathReference`
  - `Uri::isSameDocumentReference`
  - `Uri::composeComponents`
  - `UriNormalizer::normalize`
  - `UriNormalizer::isEquivalent`
  - `UriResolver::relativize`
* Deprecated `Uri::resolve` in favor of `UriResolver::resolve`
* Deprecated `Uri::removeDotSegments` in favor of `UriResolver::removeDotSegments`

* Fix `Uri::__toString` for network path references, e.g. `//example.…

…org`.

* Fix missing lowercase normalization for host.
* Fix handling of URI components in case they are `'0'` in a lot of places,
  e.g. as a user info password.
* Fix `Uri::withAddedHeader` to correctly merge headers with different case.
* Fix trimming of header values in `Uri::withAddedHeader`. Header values may
  be surrounded by whitespace which should be ignored according to RFC 7230
  Section 3.2.4. This does not apply to header names.
* Fix `Uri::withAddedHeader` with an array of header values.
* Fix `Uri::resolve` when base path has no slash and handling of fragment.
* Fix handling of encoding in `Uri::with(out)QueryValue` so one can pass the
  key/value both in encoded as well as decoded form to those methods. This is
  consistent with withPath, withQuery etc.
* Fix `ServerRequest::withoutAttribute` when attribute value is null.