update build due to cargo bug

.github/CONTRIBUTING.md

@@ -4,15 +4,15 @@
 ## Issues
 
 Found a bug? Got a question? Want some enhancement?<br>
-First place to go is the repository issues section and I'll try to help as much as possible.
+First place to go is the repository issues section, and I'll try to help as much as possible.
 
 ## Pull Requests
 
 Fixed a bug or just want to provided additional functionality?<br>
 Simply fork this repository, implement your changes and create a pull request.<br>
 Few guidelines regarding pull requests:
 
-* This repository is integrated with travis.ci and appveyor for continues integration.<br>
+* This repository is integrated with travis.ci and appveyor for continuous integration.<br>
 
 Your pull request build must pass (the build will run automatically).<br>
 You can run the following command locally to ensure the build will pass:
@@ -21,4 +21,4 @@ You can run the following command locally to ensure the build will pass:
 cargo make ci-flow
 ````
 
-* There are many automatic unit tests as part of the library which provide full coverage of the functionality.<br>Any fix/enhancement must come with a set of tests to ensure its working well.
+* There are many automatic unit tests as part of the library which provide full coverage of the functionality.<br>Any fix/enhancement must come with a set of tests to ensure it's working well.

.travis.yml

@@ -4,6 +4,7 @@ rust:
   - stable
   - beta
   - nightly
+  - 1.23.0
   - 1.22.0
   - 1.21.0
   - 1.20.0
@@ -18,3 +19,6 @@ env:
 script:
   - cargo install --debug cargo-make
   - cargo make ci-flow
+matrix:
+  allow_failures:
+  - rust: nightly