Merge pull request #1 from AsyncHttpClient/master

Merging from original repo on 3/28
[master] + minor updates
[master] + integrate Grizzly 2.3.13
Port #563 on master
New URL
Have one central place for configuration defaults, close #565
Only trigger IdleChannelDetector when maxIdleTime is > 0, close #566
Use Java8 ConcurrentHashMap backport
 [master] fix issue #564
https://github.com/AsyncHttpClient/async-http-client/issues/564
"emtpy HTTP delete message is sent using chunked transfer-encoding for no reason"
Curse people setting public modifier on interface methods
minor clean up
Release 1.8.10
Merge pull request #2 from AsyncHttpClient/master

Merging from main OSS
Making changes so that asynchttpclient config default values are picked up from the asynchttpclient.properties in case they are not specified via system property.
The search order for the default value for each config property is as such:
1. System Property
2. Property specified in asynchttpclient.properties
3. Default Value specified in code

Also introducing JMockit for unit testing.
Making changes so that asynchttpclient config default values are picked up from the asynchttpclient.properties in case they are not specified via system property.
The search order for the default value for each config property is as such:
1. System Property
2. Property specified in asynchttpclient.properties
3. Default Value specified in code

Also introducing JMockit for unit testing.
Make NPE message more explicit when passing a null hostname to avoid proxy, close #560, close #561
RequestBuilder.setUrl shouldn't accept an URI without a host, close #571
minor clean up, properly use NPE instead of IAE
Minor ProxyUtils.matchNonProxyHost clean up, still very incomplete
Ensure certificate verification by using a singleton.