Adding the initial documentation

_pages/docs/quick-start-guide.md

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+---
+layout: single
+title : "Documentation"
+author_profile: false
+excerpt: "Quick start guide"
+header:
+  overlay_color: "#5DADE2"
+permalink: /docs/quick-start-guide/
+sidebar:
+  nav : docs
+---
+{% include toc icon="gears" title="Quick-start" %}
+
+Please send all pull requests to the `develop` branch.
+{: .notice--warning}
+
+## Quick start
+First, start by cloning the repository:
+
+``` bash
+git clone https://github.com/paboyle/Grid.git
+```
+
+Then enter the cloned directory and set up the build system:
+
+``` bash
+cd Grid
+./bootstrap.sh
+```
+
+Now you can execute the `configure` script to generate makefiles as in this example (here from a build directory):
+
+``` bash
+mkdir build
+cd build
+../configure --enable-precision=double --enable-simd=AVX --enable-comms=mpi-auto --prefix=<path>
+```
+
+where `--enable-precision=` sets the default precision,
+`--enable-simd=` sets the SIMD type, `--enable-
+comms=`, and `<path>` should be replaced by the prefix path where you want to
+install Grid (optional). Other options are detailed in the next section, you can also use `configure
+--help` to display them. Like with any other program using GNU autotool, the
+`CXX`, `CXXFLAGS`, `LDFLAGS`, ... environment variables can be modified to
+customise the build.
+
+Finally, you can build and install Grid:
+
+``` bash
+make
+make install   #this is optional
+```
+
+To minimise the build time, only the tests at the root of the `tests` directory are built by default. If you want to build tests in the sub-directory `<subdir>` you can execute:
+
+``` bash
+make -C tests/<subdir> tests
+```
+
+## Build configuration options
+
+A full list of configurations options is available with the `./configure --help` command: 
+
+Here we report the more common ones. 
+
+- `--prefix=<path>`: installation prefix for Grid.
+- `--with-gmp=<path>`: look for GMP in the UNIX prefix `<path>`
+- `--with-mpfr=<path>`: look for MPFR in the UNIX prefix `<path>`
+- `--with-fftw=<path>`: look for FFTW in the UNIX prefix `<path>`
+- `--enable-lapack[=<path>]`: enable LAPACK support in Lanczos eigensolver. A UNIX prefix containing the library can be specified (optional).
+- `--enable-mkl[=<path>]`: use Intel MKL for FFT (and LAPACK if enabled) routines. A UNIX prefix containing the library can be specified (optional).
+- `--enable-numa`: enable [numa first touch policy](http://queue.acm.org/detail.cfm?id=2513149) optimization (default `no`)
+- `--enable-simd=<code>`: setup Grid for the SIMD target `<code>` (default: `GEN`). [List of possible SIMD targets](/Grid/docs/simd_targets/).
+- `--enable-precision={single|double}`: set the default precision (default: `double`).
+- `--enable-precision=<comm>`: Use `<comm>` for message passing (default: `none`). [List of possible comm targets](/Grid/docs/comm_interfaces/). 
+- `--enable-rng={ranlux48|mt19937}`: choose the RNG (default: `ranlux48 `).
+- `--disable-timers`: disable system dependent high-resolution timers.
+- `--enable-chroma`: enable Chroma regression tests. A compiled version of Chroma is assumed to be present. 
+
+
+More details on the *Getting started* menu entries on the left. 
+
+
+This document was updated on November 2016. 
+{: .notice}
+