Fix crash when using --trace 10 or above

uint8_t is typedef'd to char, thus boost::lexical_cast treats it
as such instead of a number.
Ignore vim swap files
[ci skip]
[travis] Run Travis build when .travis.yml changed

- Change match pattern to include ^\.travis.yml
- Add executable file permissions for tools/prepare-commit-msg
[ci skip]
[travis] Shorten Travis CI run times

by adding --jobs to utilize multiple cores and using boost ppa packages
instead of downloading the source and building boost from scratch.

This effectively cuts the time for a Travis CI run in half.
Merge pull request #351 from afh/pull/git-hook

[travis] Run Travis build when .travis.yml changed
Merge pull request #352 from afh/pull/travis

[travis] Shorten Travis CI run times
Merge pull request #349 from afh/pull/DocTests

[test] Use --args-only option in DocTests.py
Merge pull request #346 from afh/pull/trace_level

Fix crash when using --trace 10 or above
Merge pull request #347 from afh/pull/gitignore

Ignore vim swap files
Correct no-python error messages

[ci skip]
Merge pull request #353 from afh/pull/typo

Correct no-python error messages
Bump copyright notice to 2015

The following script makes it a no-brainer:
% NEXT_YEAR=2015; ag -l 'Copyright.*Wiegley' \
  | xargs sed -i '' -e "s/\(Copyright.*\)-20[0-9]\{2\}/\1-${NEXT_YEAR}/"
Use same license text formatting in source files
Merge pull request #355 from afh/pull/copyright

Update copyright
[tests] Add examples parameter to DocTests

to only test the given examples instead of every single one.