(TK-37) Bump default request buffer size

Bump the default size of the request header buffer to 8192 as
per TK-37. Also, bump the size of the request header size to
16192, as having cookies over a certain size would cause the
request to fail with a 413 error regardless of how high the
requestHeaderBuffer was set.
Make request header size configurable

Add a new configuration option, :request-size, to the webserver
configuration. This will allow the user to increase the size
of the request header when they are sending an extremely
large cookie as part of a request, as if this is too
small, an HTTP 413 error will be returned. This should not need
to be increased except in cases with unusually large headers.
Remove large-cookie

Remove large-cookie from common.clj, as it was no longer
being used.
(TK-37) Cleanup based on PR comments

Cleanup code based on comments received on the PR. Use default
variables instead of hardcoded numbers for the requestBufferSize
and requestHeaderSize. Change the name of the key to configure
the request header size. Cleanup config tests by adding the
default request header size within expected-http-config?
and expected-https-config?. Ensure Jetty does not truncate
large header.
(TK-37) Update docs to reflect new option

Update docs to reflect the new option to configure the maximum
request header size.
Merge pull request #43 from fpringvaldsen/TK-37

(TK-37) Increase default request buffer size and make request header size configurable