list: Adding exception handling with prettier error reporting when a directory contains an invalid package
Merge pull request #79 from jbohren-forks/catch-invalid-package

list: Adding exception handling with prettier error reporting when a directory contains an invalid package
build: Added --extend argument to control env

This enables the building of a workspace against an arbitrary realized
catkin devel- or install-space which might not currently be sourced.
This is equivalent to sourcing the setup files in the given directory in
a subshell, building, and then exiting.

- The argument to `--extend` should be a path containing valid catkin
  setup files
- It prints out CMAKE_PREFIX_PATH at the top of the build command
- Calling `--extend` also implicitly enables `--force-cmake`
- Calling `--extend ""` (with an empty string) is invalid and will be
  reported in an error like specifying a path which doesn't exist.
Merge pull request #58 from jbohren-forks/control-parent-ws

build: Adding --extend argument to control workspace parent
build: fixup whitespace
add code format/style test and fixup code style
install flake8 with travis
Merge pull request #81 from catkin/code_style_test

add code format/style test and fixup code style
metadata: adding metadata util functions
init: creating new verb for declaring a catkin workspace by creating an empty marker file
build: Enable storing and retrieving build information from catkin tools metadata file
metadata: Switching to use .catkin_tools directory

- Metadata is stored in a `.catkin_tools` directory with a simple README
  file
- Individual yaml files are used for verb-sepcific metadata. I.e.
  `catkin build` creates/updates the file `.catkin_tools/build.yml`
- When initializing the metadata directory, the metadata module checks
  to see if that directory is contained within another
  catkin_tools-based workspace.
clean: new verb