Move calculations to outer loops for speed

Moved some things in grav_tess that could be calculated on outer loops
instead of the inner ones.
Moved things out of loops in grav_tess
Removed version badge and fix doi badge

It was lagging too much and not showing. Forgot the doi- string in doi
badge
Tweaks to bench mark code

Minor changes to the Makefile and remove the result kept. It's useless.
Added a simple Makefile to automate some tasks
Merge branch 'master' into speedup
Benchmarking more similar to topo correction
Merge branch 'master' into speedup
Precompute sin and cos of lat GLQ nodes

Gives a bit of a speedup as well.
Update changelog
Merge pull request #22 from leouieda/speedup

Speedup code by moving things out of loops
Merge branch 'master' into version-generator

Conflicts:
	.gitignore
Use versioneer to set version in doc and packages

Moved the Makefile from dist to the main Makefile. Get the version for
the docs and binary packages from print_version.py.
Tried adding a replacement string for git-archive in print_version so
that versioneer works when downloading source from github master.