Better Cython in seismic.tttime2d

Replaced lists for memoryviews of numpy arrays.
Replaced lambdas for an inlined cdef function.
General speed up of 300x. Yeah. My old code sucked.
Renamed _cttime2d.pyx to _ttime2d.pyx

Just to follow the new name convention for Cython modules.
Doesn't really make sense to have a python alternative to many modules
because they wouldn't run in a reasonable amount of time.
So modules that have no alternative _*.py module don't need the 'c' in
the beginning.
Removed parallel fwd modeling from srtomo recipes

Don't need it because of new speedups.
It's not longer a bottleneck as the serial version is 300x faster than
the old parallel version.
Updated changelog

Included entry on speedup of seismic.ttime2d
Fixed wrong link tag in seismic.ttime2d docs

It read fatiando_seismic_ttime. Missing the 2d
Merge pull request #62 from leouieda/traveltime

Better Cython for `seismic.ttime2d`
Updated changelog

Included missing entries:

* random numbers
* new `wavefd` code
* tesseroid speedup
Changed wavefd videos for scipy talk in docs
Removed the .dev in the version

This will make it easier to deploy new releases. Having the dev didn't
make much sense because 'master' is dev.
Control alpha of line in polygon plot

Added argument `linealpha` to control the transparency of the lines when
plotting a polygon. The `alpha` argument controls the transparency of
the fill.
Asking Travis CI to build docs

Trying to get Travis to run sphinx and see if it gets any errors.
Removed empty inversion.heuristic

It was causing warnings in the doc build. I'll turn on doc building in
Travis CI and make the warnings into errors. So this had to go.
Doc corrections in mesher

Doctests in mesher.Tesseroid were unindented causing an error in the
doc build.
Fixed Travis config for doc building

Added rule to clean the build binaries before building the docs and make
warnings into errors
Bugfix in Travis CI config

Forgot a -d in sphinx-build options. Have to build inplace for nosetests
to work.
Rearranged Travis config rules

Putting dependency install and doc building in `before_install` rule so
that I don't have to clean the build before running sphinx. Was having a
problem with find + rm
Forgot to backout of doc folder in Travis

Added `cd ..` to before_install rule
Merge pull request #64 from leouieda/travis

Asking Travis CI to build docs
Merge branch 'leouieda/master' into vis.mpl.wiggle

Conflicts:
	.travis.yml copied from 'leouieda/master' added obspy