Add ltsv mode

I added ltsv formatting mode with `-l` or `--ltsv` option. It prints
lines in LTSV format, and is useful for just key filtering.

Coloring is off in this mode because coderay currently doesn't support
LTSV.
Merge pull request #1 from a2ikm/ltsv-mode

Add ltsv mode
add option infomation
add option infomation
move core extension class
add travis-ci config file
add test version to 1.9.3 and 2.0.0
add badge
append coverage
change travis-ci budge
change travis-ci budge
update version
use RSpec instead of minitest/spec because minitest is not include ruby 1.8.7
change rake command for rspec
Merge pull request #3 from Tomohiro/rspec

Use RSpec instead of minitest/spec because minitest is not include ruby 1.8.7