Merge pull request #5 from google/fix_readme

Rename README.txt to README.md and use markdown formatting.

README.txt → README.md

 Protocol Buffers - Google's data interchange format
+===================================================
+
 Copyright 2008 Google Inc.
+
 https://developers.google.com/protocol-buffers/
 
 C++ Installation - Unix
-=======================
+-----------------------
 
 If you get the source from github, you need to generate the configure script
 first:
@@ -33,7 +36,7 @@ Proceed at your own risk.
 
 For advanced usage information on configure and make, see INSTALL.txt.
 
-** Hint on install location **
+**Hint on install location**
 
   By default, the package will be installed to /usr/local.  However,
   on many platforms, /usr/local/lib is not part of LD_LIBRARY_PATH.
@@ -45,7 +48,7 @@ For advanced usage information on configure and make, see INSTALL.txt.
   If you already built the package with a different prefix, make sure
   to run "make clean" before building again.
 
-** Compiling dependent packages **
+**Compiling dependent packages**
 
   To compile a package that uses Protocol Buffers, you need to pass
   various flags to your compiler and linker.  As of version 2.2.0,
@@ -83,7 +86,7 @@ For advanced usage information on configure and make, see INSTALL.txt.
   If you only want protobuf-lite, substitute "protobuf-lite" in place
   of "protobuf" in these examples.
 
-** Note for cross-compiling **
+**Note for cross-compiling**
 
   The makefiles normally invoke the protoc executable that they just
   built in order to build tests.  When cross-compiling, the protoc
@@ -106,7 +109,7 @@ For advanced usage information on configure and make, see INSTALL.txt.
   has the same version as the protobuf source code you are trying to
   use it with.
 
-** Note for Solaris users **
+**Note for Solaris users**
 
   Solaris 10 x86 has a bug that will make linking fail, complaining
   about libstdc++.la being invalid.  We have included a work-around
@@ -116,7 +119,7 @@ For advanced usage information on configure and make, see INSTALL.txt.
 
   See src/solaris/libstdc++.la for more info on this bug.
 
-** Note for HP C++ Tru64 users **
+**Note for HP C++ Tru64 users**
 
   To compile invoke configure as follows:
 
@@ -125,7 +128,7 @@ For advanced usage information on configure and make, see INSTALL.txt.
   Also, you will need to use gmake instead of make.
 
 C++ Installation - Windows
-==========================
+--------------------------
 
 If you are using Microsoft Visual C++, see vsprojects/readme.txt.
 
@@ -133,7 +136,7 @@ If you are using Cygwin or MinGW, follow the Unix installation
 instructions, above.
 
 Binary Compatibility Warning
-============================
+----------------------------
 
 Due to the nature of C++, it is unlikely that any two versions of the
 Protocol Buffers C++ runtime libraries will have compatible ABIs.
@@ -147,7 +150,7 @@ static libraries only using:
     ./configure --disable-shared
 
 Java and Python Installation
-============================
+----------------------------
 
 The Java and Python runtime libraries for Protocol Buffers are located
 in the java and python directories.  See the README file in each
@@ -156,7 +159,7 @@ Note that both of them require you to first install the Protocol
 Buffer compiler (protoc), which is part of the C++ package.
 
 Usage
-=====
+-----
 
 The complete documentation for Protocol Buffers is available via the
 web at: