Fixing SSLHandshake issue while accessing api.indix.com

[ashwanthkumar]

• Added DST_Root_CA_X3.der cert file to the repo
• Adding the above cert to truststore and creating a SSLContext out of that, which is then used while creating the default HTTPClient.
• Added methods to plug in custom implementations of Apache's ClosableHTTPClient.

cc: @ind9/analytics @arijit-indix @praveenselvam

[ashwanthkumar]

Please note still change still wouldn't work on Lolipop or any older version of Android yet.

[ashwanthkumar]

Just made some changes to make it work on Android as well. Verified it on Android level 22 - running the official Lollipop image. It needs some changes, which is also documented in the "Known issues" section of README.

[praveenselvam]

@ashwanthkumar: Thanks for this. Will work on testing it out before closing.

[bbala-github]

@ashwanthkumar shouldn't we bump up the client version as well?

[ashwanthkumar]

@bbala-github Was not sure if we're going to make any changes on top of this - that's why didn't do a client version upgrade. May be I should have been working on a SNAPSHOT version - will fix that as part of the next release.