Fixed bug with 'run test' where tests at bottom of file won't run.

The line of code starting with sublime.Region(... was hard-coding a region based on the current position minus 8000 characters. However in situations where the code file has much more than 8000 characters (say 400 lines of test code for example) tests towards the bottom of the file won't run because the resulting text_string will not contain the beginning of the class, which the code will try to find.
Removed file_character_end, as that was not correctly representing the data.

Instead just used line_region.end. This now makes the code more clear. We want to start at the beginning of the code file and go to the character position at the end of the line_region to form our text_string.
Merge pull request #5 from mspinelli/patch-1

Fixed bug with 'run test' where tests at bottom of file won't run.