Better handling of warnings from Meteor bundle

Breaking changes:

• The --prelease option has been removed

All output from Meteor to stderr is now treated as a warning. The output is
reported to the user, but the demeteorization process is not exited unless the
command exits with a non-zero code.

This release also corrects an issue where $ meteor --version would include
much more than just the version of Meteor.

Closes #80 and miscellaneous issues reported on the Modulus CLI.

Updated to handle when Meteor is not installed

This is a patch related to #76 that adds error output that makes sense
when demeteorizer fails to get the current meteor version. This problem
only happens when meteor is not installed.

This release also introduces unit tests for all functionality that has
changed or been refactored.

Fixes issues with invalid modules

• Excludes aws-sdk-browser-builder from generated package.json
• Excludes modules with version not available on npm (i.e. 0.0.0 and 0.0.0-unreleasable)
• Demeteorizer now exits with code 1 when exiting with an error

This release closes #70 #71 #72 and #73.

Corrects an issue with `--prerelease` and `--debug`

• Fixes --prerelease and --debug
• Fixes an issue with usage v0.4.12 (sets the dependency to 0.4.13 when 0.4.12 is present)

Adds support for Meteor 0.9.x

Demeteorizer now correctly converts Meteor applications at 0.9.x. Maintains support for Meteor 0.8.x. Now deletes the output folder if it exists.

This release closes #64 and #65