delete completions.py - removing . from word_separators leads to unexpec...

Removing `.` from `word_separators` leads to unexpected and unwanted behavior - when double-clicking on `Property` in either of the two lines of code below
```lua
Object.Property.field;
Object.Property:FunctionName();
```
when using Sublime Text 2, all of the first line up to the ending semi-colon `;` is selected, and in the second line `Object.Property` is selected. This is not expected behavior in keeping with Sublime's actions when using other languages/syntaxes, and should be removed. This shouldn't be necessary to assist with completions.

This pull request is in response to [this question](http://stackoverflow.com/questions/24000282/sublime-text-selection-using-lua-love2d) on StackOverflow.