Add travis config file according to hadley/devtools

* See
https://github.com/hadley/devtools/blob/b094f87fd62307f2b2b4347dfee1a9819e1004d7/.travis.yml
Add man files and NAMESPACE

* need these for build since we don't get to build the package on
  travis with existing setup - though that would be cool.
Bump version for development

* since it is compared to CRAN version
Add travis build shield
Merge branch 'travis'

* travis:
  Add travis build shield
  Bump version for development
  Add man files and NAMESPACE
  Add travis config file according to hadley/devtools
dev: switch to roxygen2 v3
dev: add rstudio project file + appropriate gitignore
Add set_leaf_colours()
Bump version to 0.1-3