Merge pull request #93 from andreialecu/refactor-apicleanup3

Version 4.0 with api refactoring and dynamic tabs.

BREAKING CHANGES:

createCollapsibleTabs() no longer exists. Instead the library exports different components (Container, Tab, ScrollView, ListView) which can be nested like normal react components.
refMap no longer exists, and creating refs is no longer necessary (it's all handled internally)
ScrollView/FlatList now forward their refs, so the caller can just tap into their ref prop
the existing onIndexChange was renamed to onTabChange, and a separate onIndexChange was implemented that just returns the new index (as a number)
diffClampEnabled was changed to revealHeaderOnScroll
redundant prop snapEnabled was removed, instead snapThreshold is number | null | undefined. If not a number, then snap is not enabled. Setting it to 0.5 will result in snapping in the middle, like in the previous version.

Fixes: #100, #98, #94, #88

.eslintrc.js

@@ -11,9 +11,10 @@ module.exports = {
     // 'react-native/no-color-literals': 'warn',
     // 'react-native/no-raw-text': 'warn',
     // 'react-native/no-single-element-style-arrays': 'warn',
+    'import/no-default-export': 'error',
   },
   plugins: ['react-native-globals', 'react-native'],
-  extends: 'universe/native',
+  extends: ['universe/native'],
   env: {
     'react-native-globals/all': true,
   },