Add 'like' functionality in where clause

[jsixface]

Fixes may be first part of #59

gitql 'select message, author from commits where message like "%author%"'
+--------------------------------+----------+
|            message             |  author  |
+--------------------------------+----------+
| support for full_message,      | cloudson |
| message, author, committer     |          |
+--------------------------------+----------+

[luizperes]

Hey @jsixface, I will check this one later as it has some file conflicts, ok?

[jsixface]

@luizperes The conflicts are due to the previous pull requests.
The changes on that pull request and this one overlap. I'll fix them

[luizperes]

Thank you @jsixface, sorry, I haven't had the time to check your PR. Will try to do it over the weekend! :)

[jsixface]

@luizperes Sure. No hurry.

[luizperes]

Hi @cloudson, what do you think about that? :)

[filhodanuvem]

It looks good for me, but I'm not sure about run like statement using escaped %.
Anyway, I'm going to test it manually.

Thanks @jsixface

[luizperes]

Sounds good @cloudson, please update us back :) thanks!

[filhodanuvem]

Here I am. The Code is good for me @jsixface .
Sorry for the delay to check it.
I've tried to create a test with the literal % char and its failed but we can in another PR work on it.