Add. show_tag() method.

Change-Id: I38b04708330300b75ee1d32f5b7992399990a330
Fix. Call communicate() on Popen objects to block on preocess completion.

Change-Id: I7ba86b3f9ba8b5e1c9f3ae6b5484dd1754bc54a2
Fix. Popen calls fail when commands contain pipes. Fixed in diff().

Change-Id: I98bc4298fbc4ba924732533dcd9ad24ceef7327b
Fix. Popen calls fail when commands contain pipes. Fixed in show_tag().

Change-Id: Idb8fcbdb76eb0666b37558296b81aad7268ddc4a
Add. import reference to json module.

Change-Id: I69cdd4391f7aca53899dc0d9432c0d3e9595d499
Fix. stream for stdout, stderr in Popen call in show_tag.

Change-Id: I9205b6abe5b14cdb4ae18332f51afaa6b96d43a6
Fix. Pep-8 compliance.

Change-Id: Ib89532afcb61f45c81d05bef6f24016097d0fd0b