Update README.md

Author: Luca Denti

README.md

@@ -1,8 +1,14 @@
 # SGAL
 
-Splicing Graph ALigner
+Splicing Graph ALigner (SGAL) performs an accurate approximate mapping of RNA-seq reads against a graph representing the transcripts of a gene.
 
-Clone and compile with
+This version is the one submitted to AlCoB 2017 (http://grammars.grlmc.com/AlCoB2017/).
+
+### Prerequisites
+  * python3 (maybe also python is good enough but I didn't test it)
+  * python3 modules: biopython, bcbio-gff, editdistance
+
+### Compiling
 ```bash
 git clone --recursive https://github.com/AlgoLab/galig.git
 cd galig
@@ -12,4 +18,6 @@ cd example/
 ./run genomic.fa annotation.gff rna_seqs.fa 3 5 gene out
 ```
 
+This version has been tested on 64bit Linux system.
+
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