Added travis badge and modified travis file to only compile/test for master branch.

.travis.yml

@@ -2,15 +2,21 @@ language: rust
 jobs:
   include:
     - stage: compile
+      if: branch = master
       cache: cargo
       before_install:
         - rustup component add rustfmt --toolchain stable-x86_64-unknown-linux-gnu
       script:
         - cargo build --verbose --all
+      on:
+        branch: master
 
     - stage: test
+      if: branch = master
       cache: cargo
       script: cargo test --verbose --all
+      on:
+        branch: master
 
     - stage: deploy-releases
       cache: cargo

README.md

@@ -2,6 +2,7 @@
 [![Crates.io](https://img.shields.io/crates/v/kalk_cli)](https://crates.io/crates/kalk_cli)
 [![GitHub](https://img.shields.io/github/license/PaddiM8/kalk)](https://github.com/PaddiM8/kalk/blob/master/LICENSE)
 [![Docs.rs](https://docs.rs/kalk/badge.svg)](https://docs.rs/kalk/latest/kalk/)
+![Build status](https://travis-ci.org/PaddiM8/kalk.svg?branch=master)]
 
 Kalk is a calculator (both program and library) that supports user-defined variables and functions.