Update README with detailed bed_seq_file description

Clarified comment for bed_seq_file parameter in README.

Author: yztxwd

README.md

@@ -118,7 +118,7 @@ concept_fscores_dataframe, motif_cav_trainers, bed_cav_trainer = run_tpcav(
     motif_file_fmt='meme',  # specify your motif file format, either meme or consensus (tab delimited file in form [motif_name, consensus_sequence])
     genome_fasta=genome_fasta,
     num_motif_insertions=[12, 24, 36],
-    bed_seq_file=bed_seq_concept, 
+    bed_seq_file=bed_seq_concept,  # bed file is provided as source for sequence concepts, if you are providing them as chromatin concepts, use bed_chrom_file option instead and provide your bigwig files using bws option
     output_dir="test_run_tpcav_output/",
     input_transform_func=transform_fasta_to_one_hot_seq,
     p=4) # number of concurrent SGDClassifier can be run at the same time, increase it if you have available CPU power, it speeds up training significantly