Fix inferred `pull-request` head for usernames with capital letters

Fixes #1256

features/pull_request.feature

@@ -630,6 +630,24 @@ BODY
     When I successfully run `hub pull-request -m hereyougo`
     Then the output should contain exactly "the://url\n"
 
+  Scenario: Create pull request from branch on the personal fork, capitalized
+    Given the "origin" remote has url "git://github.com/LightAlf/FirstRepo.git"
+    And the "Kristinita" remote has url "git@github.com:Kristinita/FirstRepo.git"
+    And I am on the "add-py3kwarn" branch pushed to "Kristinita/add-py3kwarn"
+    And I am "Kristinita" on github.com with OAuth token "OTOKEN"
+    Given the GitHub API server:
+      """
+      post('/repos/LightAlf/FirstRepo/pulls') {
+        assert :base  => 'master',
+               :head  => 'Kristinita:add-py3kwarn',
+               :title => 'hereyougo'
+        status 201
+        json :html_url => "the://url"
+      }
+      """
+    When I successfully run `hub pull-request -m hereyougo`
+    Then the output should contain exactly "the://url\n"
+
   Scenario: Create pull request to "upstream" remote
     Given the "upstream" remote has url "git://github.com/github/coral.git"
     And I am on the "master" branch pushed to "origin/master"

github/localrepo.go

@@ -57,7 +57,7 @@ func (r *GitHubRepo) remotesForPublish(owner string) (remotes []Remote) {
 	if owner != "" {
 		for _, remote := range r.remotes {
 			p, e := remote.Project()
-			if e == nil && strings.ToLower(p.Owner) == owner {
+			if e == nil && strings.EqualFold(p.Owner, owner) {
 				remotesMap[remote.Name] = remote
 			}
 		}