DOC Add a warning note wrt easy mistake

This is an easy mistake to make and SemiBin should give a better error,
but for now, add a warning in the docs.

/cc #174

Author: luispedro

docs/aemb.md

@@ -37,6 +37,8 @@ Run SemiBin2 for this sample using the `single_easy_bin` subcommand:
 SemiBin2 single_easy_bin -i contig.fa -a sample1_*.tsv -o aemb_output/sample1
 ```
 
+⚠️: You should be binning the original contigs, **not** the split contigs.
+
 This will generate the bins in the `aemb_output/sample1` directory.
 
 Note that—from SemiBin2's point-of-view—this is still single sample binning even if the abundance information is generated from multiple samples as the assembly is from a single sample.