Add Travis-CI support

This pulls in the test data from its github repository, and checks that
"make check" is succcessful.  Currently, this doesn't check the Java
support, but is a good start.
Merge pull request #9 from snowballstem/travis-ci

Add Travis-CI support
Merge pull request #8 from vstakhov/master

Add cmake build script.
Fix comment typo

Reported by Veres Lajos via Xapian.
Fix comment typo

Reported by Veres Lajos via Xapian.
Report errors prefixed by "<file>:<line>:"
Factor out location of data files.

Default it to being ../snowball-data, as it will be by default if the
git repo for it is cloned into a sibling directory.
Fix typos
Clean up casting away of const
Clean up compilation flags for generated files

Avoid duplicate -O2; enable warnings flags.
Comment fix

We don't include <stdio.h> for main.
More const clean up
Conditionalise more on DISABLE_JAVA
Avoid silent truncation of character values

Characters above Latin-1 would previously be silently truncated to their
bottom 8 bits by b_to_s().
Whitespace tweaks
Add more references to source file via ~C
Create .gitignore file