Documentation/gitweb: trivial English fixes

Change "it's" to "its" where a possessive is intended.  Also add two
missing "the" that were noticed by Ben Walton.

Signed-off-by: David Waitzman <djw@bbn.com>

Documentation/gitweb.txt

@@ -14,7 +14,7 @@ gitweb.
 
 DESCRIPTION
 -----------
-Gitweb provides a web interface to git repositories.  It's features include:
+Gitweb provides a web interface to git repositories.  Its features include:
 
 * Viewing multiple Git repositories with common root.
 * Browsing every revision of the repository.
@@ -60,7 +60,7 @@ to gitweb.  The list of projects is generated by default by scanning the
 more exact; gitweb is not interested in a working area, and is best suited
 to showing "bare" repositories).
 
-The name of repository in gitweb is path to it's `$GIT_DIR` (it's object
+The name of the repository in gitweb is the path to its `$GIT_DIR` (its object
 database) relative to `$projectroot`.  Therefore the repository $repo can be
 found at "$projectroot/$repo".