improve documentation

Matthieu correctly points out the documentation was a little sparse.
Add information about what one does after installing the repo: kind of a
spack crash course.

README.md

@@ -7,7 +7,7 @@ For more about spack and what you can do with it, spack has lots of
 [documentation](https://spack.readthedocs.io/en/latest/) and a good
 [tutorial](https://spack.readthedocs.io/en/latest/tutorial_sc16.html).
 
-## Installation
+## Repo Installation
 
 Once you've set up spack itself, you need to teach it about this collection
 ('repository' in spack lingo) of pacakges.  Go to the top-level directory of
@@ -18,3 +18,75 @@ this project and execute the following command:
 Did it work?
 
     spack repo list
+
+## Mochi Suite Installation
+
+To build the entire mochi suite with the default configuration (mercury using
+CCI's TCP transport), simply build margo:
+
+    spack install margo
+
+
+### System boost vs. spack boost
+
+The largest dependency for Mercury is the Boost package.  If your system
+already has Boost, you can teach spack about it and other
+[system packages](https://spack.readthedocs.io/en/latest/getting_started.html#system-packages).
+
+Let's say you installed Boost through your distribution (an RPM or DEB package)
+To inform spack about Boost you e.g. installed from an RPM, you would add it to
+`~/.spack/packages.yaml`
+
+```
+packages:
+    boost:
+        paths:
+            boost@system: /usr
+        version: [system]
+        buildable: False
+```
+
+## Using Mochi Suite
+
+One consequence of the spack design (where packages are installed into a prefix
+based on a hash of their configuration and compiler) is that library and header
+paths are unwieldy.  An environment-managment tool such as `moudles` helps a
+lot here, and is nicely integrated into spack:
+
+```
+ module avail
+
+ --- /blues/gpfs/home/robl/src/spack/share/spack/modules/linux-centos6-x86_64 ---
+ abtsnoozer-master-gcc-4.7.2-4ygmjep libev-4.24-gcc-4.7.2-ddpazlc
+ argobots-master-gcc-4.7.2-4wxy6p3   libsigsegv-2.10-gcc-4.7.2-vtvikjs
+ autoconf-2.69-gcc-4.7.2-a2clqmr     libtool-2.4.6-gcc-4.7.2-nxthahu
+ automake-1.15-gcc-4.7.2-bfjmuzz     m4-1.4.18-gcc-4.7.2-hftmdfw
+ boost-1.63.0-gcc-4.7.2-ds3fbl3      margo-master-gcc-4.7.2-uy4in2w
+ bzip2-1.0.6-gcc-4.7.2-jehobzs       mercury-master-gcc-4.7.2-eiyjtqs
+ cci-2.0-gcc-4.7.2-5y6vgzq           zlib-1.2.10-gcc-4.7.2-w53w2nl
+ ...
+```
+
+Load the margo module into your environment:
+
+    module add margo-master-gcc-4.7.2-uy4in2w
+
+The dependency resolution does not appear to be automatic (perhaps RobL needs
+to adjust or declare runtime depenencies?), so you'll have to
+add mercury, argobots, and abt-snoozer by hand as well.
+
+```
+ module list
+Currently Loaded Modulefiles:
+  1) margo-master-gcc-4.7.2-uy4in2w
+  2) mercury-master-gcc-4.7.2-eiyjtqs
+  3) abtsnoozer-master-gcc-4.7.2-4ygmjep
+  4) argobots-master-gcc-4.7.2-4wxy6p3
+```
+
+The modules framework will update the `PKG_CONFIG_PATH` for you:
+
+```
+ pkg-config --cflags margo
+ -I/blues/gpfs/home/robl/src/spack/opt/spack/linux-centos6-x86_64/gcc-4.7.2/argobots-master-4wxy6p3thpyhwgo67t6icducpy3ik6y5/include -I/blues/gpfs/home/robl/src/spack/opt/spack/linux-centos6-x86_64/gcc-4.7.2/abtsnoozer-master-4ygmjeptxkfddgojrupre624olf2w6mq/include -I/blues/gpfs/home/robl/src/spack/opt/spack/linux-centos6-x86_64/gcc-4.7.2/mercury-master-eiyjtqsdv6yynaylgtm5g7jib7fvnshh/include -I/blues/gpfs/home/robl/src/spack/opt/spack/linux-centos6-x86_64/gcc-4.7.2/boost-1.63.0-ds3fbl3vdsk6u5soirxcdoe3e6dw3iwx/include -I/blues/gpfs/home/robl/src/spack/opt/spack/linux-centos6-x86_64/gcc-4.7.2/cci-2.0-5y6vgzqccmk7n7vehrrcxl5ogukwv3gh/include -I/blues/gpfs/home/robl/src/spack/opt/spack/linux-centos6-x86_64/gcc-4.7.2/margo-master-uy4in2w6xniwn43iio7h6ko3j6hbxvfr/include
+ ```