Allow Exception object in _error struct.
.
missing import of TypeTuple
Fix typo in LogLevel documentation
Set dependency to openssl as ">="
Fix problems deserializing Bson long into int

Adds the ability to deserialize a Bson long into a native int. This could be problematic for numbers outside the range of int but it should probably be checked by the developer if they are taking Bson input. This caused quite a headache when we have data coming from a Json api and wanted to merge with the Bson from MongoDB before deserializing.

This code previously did not work:

```D
	int dest;

	auto jsonSource = Json(2048); // Imagine this came from a web request
	assert(jsonSource.type == Json.Type.int_); // The Json type is int

	auto source = Bson.fromJson(jsonSource); // We could do this so we can merge with a Bson object loaded from the database
	assert(source.type == Bson.Type.long_); // The Bson object now has a long

	dest.deserializeBson(source); // This caused an error as there is was conversion from long to int

```
Bson: Added assertion when trying to coorce out of range long into an int.
Avoid unecessary HTTPMethod -> string -> HTTPMethod conversion
Merge pull request #921 from Geod24/httpmethod-optimization

Avoid unecessary HTTPMethod -> string -> HTTPMethod conversion
Merge pull request #910 from Geod24/fix-openssl-upgrade

dub upgrade doesn't upgrade openssl
Merge pull request #909 from Marenz/patch-2

Fix typo in LogLevel documentation
Merge pull request #907 from MartinNowak/import

missing import of TypeTuple
Merge pull request #900 from aka-demik/master

Don't try to source _error parameters from req.params.
Merge pull request #913 from intrica/fix-bson-deserialize-long

Fix problems deserializing Bson long into int