Adds support to show Conda environment on prompt

When one uses a Virtualenv environment, its name is shown in the prompt.
The same did not happen with a Conda environment. This fix it.
Merge pull request #57 from gabraganca/conda

Adds support to show Conda environment on prompt
Implemented the possibility for an indicator which shows the result of the last command.
To enable just write

export GIT_PROMPT_SHOW_LAST_COMMAND_INDICATOR=1

just before sourcing the gitprompt.sh

fixes #60
Merge remote-tracking branch 'upstream/master'