MINOR: trim environment variable values (#79)

When working on #78, I was hit by a test failing on linux (debian host)
Our code is triming values so we need to adjust the test code to make
sure we also trim values before doing the comparison.

Example:
```
	expected: "${debian_chroot:+($debian_chroot)}\\u@\\h:\\w\\$ "
	            	actual: "${debian_chroot:+($debian_chroot)}\\u@\\h:\\w\\$"
```

CHANGELOG.md

@@ -7,6 +7,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 ### Added
 
 ### Changed
+- Fixed Trim environment variables when comparing values in the test suite. #79
 
 ### Deprecated
 

sigar_interface_test.go

@@ -5,6 +5,7 @@ import (
 	"os/user"
 	"path/filepath"
 	"runtime"
+	"strings"
 	"testing"
 	"time"
 
@@ -134,7 +135,7 @@ func TestProcEnv(t *testing.T) {
 		assert.True(t, len(env.Vars) > 0, "env is empty")
 
 		for k, v := range env.Vars {
-			assert.Equal(t, os.Getenv(k), v)
+			assert.Equal(t, strings.TrimSpace(os.Getenv(k)), v)
 		}
 	}
 }