replace some quotes in command's banners

to prevent broken syntax highlighting in emacs (and maybe in another
editors too)

lib/cocoapods/command/install.rb

@@ -6,15 +6,14 @@ module Pod
 
     $ pod install [PROJECT]
 
-      Downloads all dependencies defined in `Podfile' and creates an Xcode
-      Pods library project in `./Pods'.
+      Downloads all dependencies defined in 'Podfile' and creates an Xcode
+      Pods library project in './Pods'.
 
-      In case `PROJECT' is given, it configures it to use the specified Pods
-      and generates a workspace with the Pods project and `PROJECT'. (It is
+      In case 'PROJECT' is given, it configures it to use the specified Pods
+      and generates a workspace with the Pods project and 'PROJECT'. (It is
       important that once you have run this you open the workspace instead of
-      `PROJECT'.) You usually specify `PROJECT' only the first time that you
-      run `pod install'.
-}
+      'PROJECT'.) You usually specify 'PROJECT' only the first time that you
+      run 'pod install'.}
       end
 
       def self.options

lib/cocoapods/command/repo.rb

@@ -8,13 +8,13 @@ module Pod
 
     $ pod repo add NAME URL
 
-      Clones `URL' in the local spec-repos directory at `~/.cocoapods'. The
-      remote can later be referred to by `NAME'.
+      Clones 'URL' in the local spec-repos directory at '~/.cocoapods'. The
+      remote can later be referred to by 'NAME'.
 
     $ pod repo update NAME
 
-      Updates the local clone of the spec-repo `NAME'. If `NAME' is omitted
-      this will update all spec-repos in `~/.cocoapods'.}
+      Updates the local clone of the spec-repo 'NAME'. If 'NAME' is omitted
+      this will update all spec-repos in '~/.cocoapods'.}
       end
 
       extend Executable

lib/cocoapods/command/search.rb

@@ -6,8 +6,8 @@ module Pod
 
     $ pod search [QUERY]
 
-      Searches for pods, ignoring case, whose name matches `QUERY'. If the
-      `--full' option is specified, this will also search in the summary and
+      Searches for pods, ignoring case, whose name matches 'QUERY'. If the
+      '--full' option is specified, this will also search in the summary and
       description of the pods.}
       end
 

lib/cocoapods/command/setup.rb

@@ -6,8 +6,8 @@ module Pod
 
     $ pod setup
 
-      Creates a directory at `~/.cocoapods' which will hold your spec-repos.
-      This is where it will create a clone of the public `master' spec-repo from:
+      Creates a directory at '~/.cocoapods' which will hold your spec-repos.
+      This is where it will create a clone of the public 'master' spec-repo from:
 
           https://github.com/CocoaPods/Specs
 

lib/cocoapods/command/spec.rb

@@ -6,12 +6,12 @@ module Pod
 
     $ pod spec create NAME
 
-      Creates a PodSpec, in the current working dir, called `NAME.podspec'.
+      Creates a PodSpec, in the current working dir, called 'NAME.podspec'.
 
     $ pod spec lint NAME.podspec
 
-      Validates `NAME.podspec'. In case `NAME.podspec' is omitted, it defaults
-      to `*.podspec' in the current working dir.}
+      Validates 'NAME.podspec'. In case 'NAME.podspec' is omitted, it defaults
+      to '*.podspec' in the current working dir.}
       end
 
       def initialize(argv)