Update README.md

Default METADATA.jl is not empty.
Merge pull request #36 from lgautier/patch-1

Update README.md
Trivial corrections to README
documentation for adding new packages
Merge pull request #37 from lgautier/patch-2

README: More Pkg documentation
Add HDF5 package
Enhance the instructions for creating new packages.
Add MAT package
Merge pull request #38 from simonster/master

Add MAT package
DataFrames version bump
adding GLU, GLUT, OpenGL, SDL, and GetC
Update Debug: Conditional breakpoints, more interpolation, ...
bump Tk sha
bump Winston sha
Bump DataFrames SHA1
Merge pull request #39 from rennis250/master

OpenGL, GLUT, SDL, GLU, and GetC packages
Updated SHAs for GLU, GLUT, GetC, OpenGL, and SDL (added LICENSE and updated READMEs)
Merge pull request #40 from rennis250/master

Added LICENSEs and updated READMEs
bump Tk sha1
Bump HDF5