Fix a bug that kaminari doesn't work with nested param_name

fixes #53 but this bug still appears when kaminari is used on sinatra.
Ruby 1.8.7 doesn't like the new hash syntax...
:disappointed_relieved:
Squash "warning: ambiguous first argument; put parentheses or even spaces"
Change 'previous' to 'prev'

"previous" is treated like "prev" by most user agents(maybe), but since
"prev" is officially listed in the specification:
http://www.w3.org/TR/html5/links.html#linkTypes, it should be used
instead of the long version.
PrevPage and NextPage don't use total pages and per page values
Use NextPage and PrevPage to generate link tags for rel=next and rel=prev

fixes #535, closes #509
Add "describe 'Tag'" block
Variable name 'i' isn't a good name, it represents the number of the page
Issue #310 fixed. Refactored code to use a single method to know if a tag page should be displayed.

310 - Fixed. Need to write some tests now.

310 - Fixed. Need to write some tests now.

Stubbed Specs

All tests are passing
Merge remote-tracking branch 'upstream/master'
Another attempt to use SVG badges
Properly show the Code Climate badge

[skip ci]
Merge remote-tracking branch 'upstream/master'