Get Rid of nobuild, nolink, and alldeps (#2765)

* Removing the nobuild, nolink, and alldeps dependency types in favor of being explicit.
* This will help with maintenance going forward, as adding more dependency types won't affect existing declared dependencies in weird ways.
* default deptype is still `('build', 'link')`

var/spack/repos/builtin/packages/py-emcee/package.py

@@ -35,7 +35,7 @@ class PyEmcee(Package):
     version('2.1.0', 'c6b6fad05c824d40671d4a4fc58dfff7')
 
     extends('python')
-    depends_on('py-numpy', type=nolink)
+    depends_on('py-numpy', type=('build', 'run'))
 
     def install(self, spec, prefix):
         setup_py('install', '--prefix={0}'.format(prefix))