Remove url from translated string

An 'A' tag should not be a part of a translated string, but passed as a
parameter to a t() function.

Kindly reported by llang [1] during his review [2] of the module.

[1] http://drupal.org/user/223377
[2] http://drupal.org/node/1940516#comment-7178460
Fix a typo in variable name

Kindly reported by llang [1] during his review [2] of the module.

[1] http://drupal.org/user/223377
[2] http://drupal.org/node/1940516#comment-7178460
Fix grammatical errors in INSTALL.txt

Kindly reported by llang [1] during his review [2] of the module.

[1] http://drupal.org/user/223377
[2] http://drupal.org/node/1940516#comment-7178460