INSTALL : do not use libsvm>325
libsvm > 325 seems to crash some otb application as highlighted in #602 (closed).
Two solutions :
- ask users to use iota2-deps channel to install iota2 -> update the documentation.
- modify otb recipe at meta.yaml#L63 and meta.yaml#L85 to limit libsvm version. However maybe the bug will be corrected in the futur.