Fix for Dotless i Problem on Android

[eczmustafa]

.toLowerCase() function on an Android system with Turkish language causes a bug.

Please see: joltup#573

Error message starts with "Error RNFetchBlob request error: Unexpected char 0x131 at ...". -> 0x131 is ı (dotless i).

.toLowerCase() function works and does its job in a correct way. However, dotless i and normal i aren't considered equal, naturally.

Only workaround, as far as i can find out, is this.

[halaei]

Hello @eczmustafa
Continuing our conversation from joltup#762, I think your examples doesn't apply to the original issue. We are not supposed to assign headers with non-ascii characters to an http request. So the fact that ŞĞÜİI becomes şğüi̇i even with English locale isn't relevant. The important thing is that a valid English header like X-MOBILE-APP-VERSION should not be converted to x-mobıle-app-versıon.
So still the correct fix is setting the locale, e.g. toLowerCase(Locale.ROOT).
Also note that there are many other calls to toLowerCase() in this library and probably they need to be addressed as well.

[RonRadtke]

I implemented the fix metioned on the old repository by using the Locale.ROOT. Thus I'm closing the PR.