Merge pull request #7 from unmric/master

Notice the error when the Gruntfile.js does not exist or the node module 'grunt' does not exist.
new folder src
add gitignore
.gitignore
add grunt-node-webkit-builder
add mac icon
fix bug of drag donn't work on mac
Merge pull request #10 from willerce/develop

add nodewebkit builder and bug fix bug of drag
fix bug of tasks delete
Merge branch 'unmric-master' into develop
Merge pull request #11 from willerce/develop

fix bug of task delete
update version
Merge pull request #12 from willerce/develop

update version to 0.0.2