remove unused potential call in find lowest eigenvector algorithm
add get_state() and set_state() to LBFGS
add get_state() and set_state to MYLBFGS with tests
updates for generalized dimer
add a test for LowestEigPot
add a class FindLowestEigenvector
update generalize dimer
modifications to _generalized dimer
fix the lowest eigenvalue potential test
add first order derivative eigenvector search potential
make use of first order derivatives in FindLowestEig
add first order derivative option to hybrid eigenvector following

note that the gradient is still being recomputed at least once
per iteration in FindTransitionState
add notes for finding the smallest eigenvalue

I put it a subfolder of the doc/ folder.  We can move it later if we
want
reformulate GeneralizedDimer as a class
add a test for GeneralizedDimer
add some more notes to finding_smallest_eigenvalue.tex

make connection to dimer and Rayleigh-Ritz
add generalized hybrid eigenvector following

this uses the same framework as generalized dimer
rename a bunch of files in pele/transition_states/

add an underscore to the start of the file names

also fix a path bug in some transition state tests
eliminate unnecessary force calls in FindTransitionState
add option to FindTransitionState

the new option controls checking (and backtracking) whether eigenvalue
changes sign.  The new default behavior is that checking is turned off
which is the same default behavior as OPTIM.