Remove non-git method of building from source. Git is now a required

dependency for downloading and building julia.
Close #474
Close #486

README.md

@@ -40,10 +40,6 @@ First, acquire the source code either by cloning the git repository (requires **
 
     git clone git://github.com/JuliaLang/julia.git
 
-or, if you don't have git installed, by using wget and tar to fetch and unpack the source:
-
-    mkdir julia && wget -O - https://github.com/JuliaLang/julia/tarball/master | tar -zxf- -C julia --strip-components 1
-
 Next, enter the `julia/` directory and run `make` to build the `julia` executable.
 When compiled the first time, it will automatically download and build its [external dependencies](#Required-Build-Tools-External-Libraries).
 This takes a while, but only has to be done once.
@@ -98,8 +94,9 @@ Buliding Julia requires that the following software be installed:
 
 - **[GNU make]**                — building dependencies.
 - **[gcc, g++, gfortran][gcc]** — compiling and linking C, C++ and Fortran code.
+- **[git]**    			— contributions and version control.
 - **[perl]**                    — preprocessing of header files of libraries.
-- **[wget]** or **[curl]**          — to automatically download external libraries (Linux defaults to `wget`, OS X and FreeBSD to `curl`).
+- **[wget]** or **[curl]**      — to automatically download external libraries (Linux defaults to `wget`, OS X and FreeBSD to `curl`).
 
 With the exception of `gfortran`, these are standard on most Linux systems and on any OS X system with `Xcode` and Apple's Developer Tools installed.
 Julia uses the following external libraries, which are automatically downloaded and compiled from source (or in a few cases, included in the Julia source repository) the first time you run `make`: