Autocomplete function name with arity inside an export statement

Added code for this. It first checks if point is with an export list before removing the /x in the function auto complete.

I have tested manually in emacs but when I tried to run the integration tests I get:
```
`flet' is an obsolete macro (as of 24.3); use either `cl-flet' or `cl-letf'.
`labels' is an obsolete macro (as of 24.3); use `cl-labels' instead.
`flet' is an obsolete macro (as of 24.3); use either `cl-flet' or `cl-letf'.
`flet' is an obsolete macro (as of 24.3); use either `cl-flet' or `cl-letf'.
`flet' is an obsolete macro (as of 24.3); use either `cl-flet' or `cl-letf'.
`flet' is an obsolete macro (as of 24.3); use either `cl-flet' or `cl-letf'.
`flet' is an obsolete macro (as of 24.3); use either `cl-flet' or `cl-letf'.
Symbol's value as variable is void: erlang-operators-regexp
make: *** [ert] Error 255
```