variable name change: Twenty fifth perc. log rank (unique) -> Twenty fifth perc. log rank (unique words)

num_video_df.tsv

@@ -1,4 +1,4 @@
-Words per minute	Average sentence length	Average relative repetitions	Vocab size needed for 98% word coverage	Twenty fifth perc. log rank (unique)	Proportion of adverbs	Proportion of determiners	Proportion of nouns	Proportion of subordinating conjunctions	Proportion of wago	Proportion of gairaigo	Proportion of kango	Level
+Words per minute	Average sentence length	Average relative repetitions	Vocab size needed for 98% word coverage	Twenty fifth perc. log rank (unique words)	Proportion of adverbs	Proportion of determiners	Proportion of nouns	Proportion of subordinating conjunctions	Proportion of wago	Proportion of gairaigo	Proportion of kango	Level
 51.53095084987292	7.245283018867925	0.0128205128205128	4030	3.80666248977032	0.0331125827814569	0.0	0.1754966887417218	0.0364238410596026	0.8847457627118644	0.0576271186440678	0.0305084745762711	1
 47.06622333806611	6.672727272727273	0.015625	2807	3.73658699848178	0.0171821305841924	0.0068728522336769	0.3264604810996563	0.0	0.8503649635036497	0.0364963503649635	0.0656934306569343	1
 37.34674630619302	6.5	0.0169491525423728	2984	4.730627360117875	0.0353535353535353	0.0	0.2878787878787879	0.005050505050505	0.8465608465608465	0.0423280423280423	0.0846560846560846	1