move dependencies for email parsing to requirements.txt

install/requirements.txt

 typing==3.5.3.0
 rq==0.7.1
 click==6.7
+markdown
+email_reply_parser

tracim/setup.py

     'rq==0.7.1',
     'filedepot>=0.5.0',
     'preview-generator',
-    'beautifulsoup4',
-    'markdown',
-    'email_reply_parser',
-    'requests',
-]
+ }
 
 setup(
     name='tracim',