GTH_SOLVE: Refactored, typo corrected
DOC: graph_tools, gth_solve added to tools.rst
Merge pull request #100 from oyamad/gth_solve

Refactor gth_solve.py; add documentation of gth_solve and graph_tools
Added PW to lead developers
Merge branch 'master' of https://github.com/QuantEcon/QuantEcon.py
BUG: Fix bug for input with int elements
Merge pull request #102 from oyamad/gth_solve

BUG: Fix bug for input with int elements