Version 0.3 changes

These are the major changes to cobrapy for the v0.3. This release should include:
 - [x] faster solver interface for pyglpk, gurobi, and cplex
 - [x] using the faster solver interface for fva and single/double deletions
 - [x] cython-based glpk solver
 - [x] more flux analysis tools: pFBA and phenotypic phase planes
 - [ ] improved documentation
 - [ ] expanded unit test coverage
 - [ ] sbml fbc support
 - [x] improvements to ArrayBasedModel
 - [x] Simplify API: access read-only attributes
 - [ ] integration with zakandrewking/escher@2e4c012
 - [x] simplified installation
 - [ ] code cleanup