Rewrite installation script in fish shell.

That now means oh my fish requires fish to be installed, but this is
probably for the better.
Merge pull request #137 from xfix/install-in-fish

Rewrite installation script in fish shell.
add README file with list of plugins and their short descriptions
Merge pull request #142 from skrobul/readme-for-plugins

add README file with list of plugins and their short descriptions
Gitignore: Ignore vim backup file (sw?).
Update README with custom themes

Mention how to use custom themes by placing them in custom/themes.
Merge pull request #143 from jonathanpa/master

Ignore vim backup file (sw?) and explain use of custom themes.
Added a beloglazov theme, which is based on the default robbyrussel theme. This theme adds time, the number of non-pushed git commits, and whether the previous command has failed.
beloglazov theme: removed the "git:" prefix from the branch name to make the prompt shorter
beloglazov theme: call _git_branch_name only once - performance
Changed the indentation style to 2 spaces as requested by @bpinto
Merge pull request #141 from beloglazov/master
added integral theme
Showing the full path in the prompt.
Showing the difference of commits on upstream
Preventing error when the branch isn't on upstream
Took the extra 0 out
forgot an if
Space on the propper place
Added screenshot to the readme file.