Make HttpRequestException constructor public

This allows sub-classes easily throw it when overriding methods
in HttpRequest.

Refs #52
Added maxConnections property.
Replace tabs with spaces
Inline max connections value
Add @DavidTPate to contributors
[maven-release-plugin] prepare release http-request-5.5
[maven-release-plugin] prepare for next development iteration
Bump version to 5.5
Add license information to README
:lipstick: Tweak section headers
Add async question to FAQ
Use double quotes
Merge pull request #1 from kevinsawicki/master

Pull from origin