Enable XD commands support

Signed-off-by: Esben Haabendal <esben@haabendal.dk>
RecipeVersion class for handling XD-build recipe versions

Signed-off-by: Esben Haabendal <esben@haabendal.dk>
Hook up with Travis CI and Coveralls

Signed-off-by: Esben Haabendal <esben@haabendal.dk>
Update README.md with badges and a bit more information

Signed-off-by: Esben Haabendal <esben@haabendal.dk>
RecipeFile class for handling XD-build recipe files

Signed-off-by: Esben Haabendal <esben@haabendal.dk>