Correct IDE name spelling

Summary: Closes https://github.com/facebook/infer/pull/183

Reviewed By: @jvillard

Differential Revision: D2484305

Pulled By: @cristianoc

INSTALL.md

@@ -17,8 +17,8 @@ the dependencies installed and opam configured properly. After that either
 - Python 2.7
 - opam (instructions [here](https://opam.ocaml.org/doc/Install.html#OSX))
 - Java <= 1.7 (only needed for the Java analysis)
-- XCode <= 6.3, >= 6.1 (only needed for the C/Objective-C analysis)
+- Xcode <= 6.3, >= 6.1 (only needed for the C/Objective-C analysis)
-- clang in XCode command line tools. You can install them with the command `xcode-select --install` (only needed for the C/Objective-C analysis)
+- clang in Xcode command line tools. You can install them with the command `xcode-select --install` (only needed for the C/Objective-C analysis)
 
 ### Setup Opam