chore: update to rxjs 6 and axios 0.18

.travis.yml

@@ -5,7 +5,7 @@ cache:
   directories:
     - "node_modules"
 before_script:
-  - "npm install --no-save axios@0.17 rxjs"
+  - "npm install --no-save axios@0.18 rxjs"
 script:
   - "npm test -- -w=2"
 after_success:

README.md

@@ -6,6 +6,10 @@
 
 Rxios makes the awesome [axios](https://github.com/axios/axios) library reactive, so that it's responses are returned as [RxJS](https://github.com/ReactiveX/rxjs) observables.
 
+### RxJS 6
+
+Note that this version is build against [RxJS 6](https://github.com/ReactiveX/rxjs#rxjs-6) and your project may require migration from RxJS 5.x to RxJS 6.x.
+
 ### Observables? Why?
 
 Regular promises are cool, especially for HTTP requests in async/await functions.
@@ -95,11 +99,11 @@ All Rxios methods always return an Observable, to which we can apply advanced Rx
 For example, we could make two simultaneous requests and merge their responses as they come, without needing to wait for both to be completed.
 
 ```javascript
-import { Observable } from 'rxjs/Rx';
+import { Observable, merge } from 'rxjs';
 import { Rxios } from 'rxios';
 const http = new Rxios();
 
 const firstReq = http.get('/posts/1');
 const secondReq = http.get('/posts/2');
-firstReq.merge(secondReq).subscribe(...);
+merge(firstReq, secondReq).subscribe(...);
 ```