Misc cleanups

* Unused variables
* Use literal directly for CR character rather than variable defined in
  another place
* Thread.start() does not return anything
“from gi import pygtkcompat” deprecated
External “simplejson” module no longer used
String comparison rather than object comparison
README.md to signify markdown syntax for Git Hub
Expand slightly on the GTK API issues
Warning about metered server fallback
Extra programme fields
Parse numbers and dates
Use selection’s “changed” signal rather than tree’s “cursor-changed”

In GTK 3.4.4 and 3.6.1, the “cursor-changed” signal is triggered when the
tree is destroyed, which meant get_selection() returned None and the callback
crashed. This behaviour seems to be gone again in GTK 3.8.2.

Workaround inspired by “Changes in ‘cursor-changed’ signal of Gtk.TreeView
cause issues with netzob”, https://dev.netzob.org/issues/234.
Use GTK 3 via G Object introspection, rather than GTK 2
TreeStore.insert_with_values() workaround not required in GTK 3
Proper way to decode stderr to text
Separate line for Jeremy’s copyright claim
Only update buttons when process actually exits and is collected
Factor rtmpdump process scraping from GUI code
Size parameter in bytes; report to user in SI units (1 MB = 10^6 B)
Move RTMP scraping class to “fetch” module
Calculate fraction based on total size expected
Merge branch 'frontend' (early part) into HEAD

Conflicts:
	iview/fetch.py
	iview/parser.py