.travis.yml: Remove tests/ from py.test line
.travis.yml: Remove tests/ from py.test line

allow pytest to just scan and find tests/ rather than hardcoding it

zerolugithub/pymssql,JimDennis/pymssql,zerolugithub/pymssql,bladams/pymssql,ramiro/pymssql,ramiro/pymssql,Aloomaio/pymssql,JimDennis/pymssql,Aloomaio/pymssql,ramiro/pymssql,Aloomaio/pymssql,klothe/pymssql,bladams/pymssql,klothe/pymssql,zerolugithub/pymssql,klothe/pymssql,pymssql/pymssql,pymssql/pymssql,JimDennis/pymssql,bladams/pymssql