Init commit for j1j2 implementation.
First pass implementation for j1j2j2p chain.
Wrote version of J1J2 based on tut01

Wrote a version of J1J2 that builds the Hamiltonian rescursively from
the left in the way shown in tut01, rather than the version with right
and left blocks in tut00
Merge branch 'j1j2'

J1J2J2' chain implementation using Lanczos.
Merged j1j2 branch with master.
Added executable flag to j1j2_tut01 and tut01.