Doesn't Support TLS 1.1/1.2 on Android 4.x

[jhellman]

When using an Android 4.x device to connect to a web server that only supports TLS 1.1 and greater, React-Native-Fetch-Blob is unable to download files and fails with an error.

This is similar to a problem faced (and fixed) by the core React Native team (facebook/react-native#7192).

I've patched React-Native-Fetch-Blob in a manner similar to the fix for the core project (which is pretty straightforward since both projects use OKHttp and will open a PR soon to resolve this issue.

[wkh237]

@jhellman , thanks for the heads up. It'd be grateful if you can make a PR 👍

[jhellman]

k - I'm ready to create a PR, but the PR template wants me to direct at branch 0.10.7 but that branch doesn't yet exist.