[FIX] P3: more requirements.txt changes

- jcconv is not P3-ready and is only optional, for use on the POSBox
  firmware for Japanese charset support in some receipt printers
  (The POSBox firmware is still based on Odoo 8 + PY2 at this time)

- wsgiref is built-in since Python 2.5, and the one on pypi does not work
  on Python 3.2+

requirements.txt

@@ -5,7 +5,6 @@ ebaysdk==2.1.4
 feedparser==5.2.1
 gevent==1.1.2
 greenlet==0.4.10
-jcconv==0.2.3
 html2text==2016.9.19
 Jinja2==2.8
 lxml==3.5.0
@@ -37,7 +36,6 @@ suds-jurko==0.6
 vatnumber==1.2
 vobject==0.9.3
 Werkzeug==0.11.11
-wsgiref==0.1.2
 XlsxWriter==0.9.3
 xlwt==1.1.2
 xlrd==1.0.0