Support catchup-id attribute in programme element

[jaylinski]

Fixes #24.

[codecov]

Codecov Report

Merging #25 (8964c21) into master (9906971) will not change coverage.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##              master       #25   +/-   ##
===========================================
  Coverage     100.00%   100.00%           
  Complexity       130       130           
===========================================
  Files             33        33           
  Lines            377       378    +1     
===========================================
+ Hits             377       378    +1     

Impacted Files	Coverage Δ	Complexity Δ
src/Tv/Programme.php	100.00% <100.00%> (ø)	30.00 <0.00> (ø)

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