Added test for file extension
Update videogrep.py

Removed print statement
Improved diagnostic information
Tested support for mkv and mv4
Added ability to resync subtitle file by constant offset
Update README.md
add mkv and display error if no search terms found
Merge branch master of https://github.com/antiboredom/videogrep
Update README.md
merging @autonomoid changes
Merge branch 'autonomoid-master'
merging readme
Fixed minor bug in input validation coverage.
Removed unnecessary comment regarding output file
Merge pull request #10 from autonomoid/master

Fixed minor bug in input validation coverage.
Update README.md