Initial commit
Init commit
Fix. Detect raise error in callback
Add. HeaderFunction callback.
Fix. Export getinfo_ function.
Add. Rockspec file.
Fix. Define export functions.
Add. escape/unescape methods to easy object.
Add. version/version_info function
Update doc.
Add. Easy wrapper example
Add. `setopt` method.

```Lua
e:setopt(curl.OPT_URL, 'http://example.com')
```
Add. Travis files
Fix. Support libcurl >= 7.25
Move error codes in separate files.
Fix. Echo libcurl version in test.
Add. Export error codes
Move push_cb function to utils.
Add. ProgressFunction option
Add. Export some libcurl flags and constants.