Breaking change in v0.5.1 when using Concat on Windows

Today I've tried to update grunt-angular-templates from 0.3.10 to 0.5.5. The build failed and I traced the error back to the changes happening in v0.5.1.

I've noticed the comment by @mzgol on 7cdbd768d8b6f1f15a7d93bb458ce32a17af867d:

> This doesn't just add the `usemin` option, this removes the `concat` option as well. This is a breaking change, you should have changed the version number to `0.6.0`, patch releases shouldn't introduce breaking changes... I've just got bitten by that.

**Was concat support removed?**

Running build on Windows 7. It's running in "Git bash" (cmd with bash).

**Compare of changes in v0.5.1:**
https://github.com/ericclemmons/grunt-angular-templates/compare/v0.5.0...v0.5.1
### Output when running Grunt build

```
Running "ngtemplates" task

Running "ngtemplates:projectname" (ngtemplates) task
Verifying property ngtemplates.projectname exists in config...OK
Files: projectname/src/part1/part1.html, (...), projectname/src/part2/part2.html -> .tmp/templates.js
Options: angular="angular", bootstrap=undefined, concat="dist/projectname/scripts.js", htmlmin={"collapseBooleanAttributes":true,"collapseWhitespace":true,"removeAttributeQuotes":true,"removeComments":true,"r
emoveEmptyAttributes":true,"removeRedundantAttributes":true,"removeScriptTypeAt t
ributes":true,"removeStyleLinkTypeAttributes":true}, module={"name":"Projectname","define":false}, prefix="", source=undefined, standalone=false, url=undefined, usemin=null, base="projectname"
Options: angular="angular", bootstrap=undefined, concat="dist/projectname/scripts.js", htmlmin={"collapseBooleanAttributes":true,"collapseWhitespace":true,"removeAttributeQuotes":true,"removeComments":true,"r
emoveEmptyAttributes":true,"removeRedundantAttributes":true,"removeScriptTypeAttributes":true,"removeStyleLinkTypeAttributes":true}, module={"name":"Projectname","define":false}, prefix="", source=undefined,
standalone=false, url=undefined, usemin=null, base="projectname"
Reading projectname/src/part1/part1.html...OK
(...)
Reading projectname/src/part2/part2.html...OK
Writing .tmp/templates.js...OK
File .tmp/templates.js created.
Files: projectname/src/part1/part1.ctrl.js, (...), projectname/src/part2/part2.ctrl.js -> [no dest]
Added .tmp/templates.js to concat:dist/projectname/scripts.js

(...) OTHER TASKS (...)

Running "concat:dist/projectname/scripts.js" (concat) task
Verifying property concat.dist/projectname/scripts\.js exists in config...OK
Files: projectname/src/part1/part1.ctrl.js, (...), projectname/src/part2/part2.ctrl.js, .tmp/templates.js -> [no dest]
Options: separator="\r\n", banner="", footer="", stripBanners=false, process=false
Reading projectname/src/part1/part1.ctrl.js...OK
(...)
Reading projectname/src/part2/part2.ctrl.js...OK
Reading .tmp/templates.js...OK
Writing undefined...ERROR
Warning: Unable to write "undefined" file (Error code: undefined). Use --force to continue.

Aborted due to warnings.
```
### Configuration:

``` javascript
ngtemplates: {
projectname: {
options: {
base: '<%= yeoman.app %>',
module: {
name: 'Projectname',
define: false
},
concat: '<%= yeoman.dist %>/scripts.js',
htmlmin: {
collapseBooleanAttributes: true,
collapseWhitespace: true,
removeAttributeQuotes: true,
removeComments: true, // Only if you don't use comment directives!
removeEmptyAttributes: true,
removeRedundantAttributes: true,
removeScriptTypeAttributes: true,
removeStyleLinkTypeAttributes: true
}
},
src: '<%= yeoman.app %>/src/**/*.html',
dest: '.tmp/templates.js'
}
},
```