Update/samtools (#3595)

* Update samtools family to 1.4

* simple cleanup

* Make bzip depends_on for future versions too

var/spack/repos/builtin/packages/bcftools/package.py

@@ -34,9 +34,11 @@ class Bcftools(Package):
     homepage = "http://samtools.github.io/bcftools/"
     url      = "https://github.com/samtools/bcftools/releases/download/1.3.1/bcftools-1.3.1.tar.bz2"
 
+    version('1.4', '50ccf0a073bd70e99cdb3c8be830416e')
     version('1.3.1', '575001e9fca37cab0c7a7287ad4b1cdb')
 
     depends_on('zlib')
+    depends_on('bzip2', when="@1.4:")
 
     def install(self, spec, prefix):
         make("prefix=%s" % prefix, "all")