Return fault code and description on RPC service errors

Instead of just raising an Exception which is serialized to the client
as 'The request could not be completed', we now always raise a Fault
which is serialized as a SOAP Fault object or as a JSON object with
faultcode and faultstring properties (and HTTP 500 response status).

This fixes Trac #41.

Release 2.0.6

Fixes #24

SQLite accepted the incorrect non-aggregate use of columns missing from
the GROUP BY, whereas PostgreSQL did not.

Added batch script and windows instructions.

Discard incomplete features in genbank files

Many genbank reference files contain more than one gene, especially
slices from an assembly. Some of these genes may be incomplete in
the reference file (i.e., either start or end exceeds the outer
coordinates). We cannot really do anything with these genes, so we
discard them during parsing.

Add getGeneLocation webservice method

Given a gene symbol and optional genome build, this returns the location
of the gene.

Primary motivation for this is LOVD, where it will be used in combination
with sliceChromsome as an alternative for sliceChromosomeByGene which only
works on the fixed Ensembl genome build.

Fix error in git tag instructions

Release 2.0.5

Update documentation homepage layout

Update documentation on contributing and releases

Compilation of developer documentation on Read The Docs

We use a separate `doc/requirements.txt` file for building the
documentation. Since on Read The Docs where we cannot install
packages depending on C libraries, we mock these packages in
`doc/conf.py` and omit them from the requirements.

Add Travis CI configuration

See merge request !26