Revamp the library

[japaric]

New features:

• Add "stripe" iterators
• Add set method for operations like A[i, :] = B[j, :]
• Add splitting methods: hsplit_at[_mut], vsplit_at[_mut]
• Implement FromIterator for linear collections
• Lazy matrix (chain) product
• Matrix inversion
• Python-like slicing (minus the sugar): A[:i, j:k] => A.slice((..i, j..k))
• Solve the Matrix Chain Ordering Problem

[breaking-change]s

• replace impl Iter[Mut] for linear collections with inherent iter[_mut] functions
• remove fine error handling, i.e. panic on programmer errors
• rename Trans to Transposed
• rename [Mut]View to SubMat[Mut]
• change Scaled<T, M> to Scaled<M: Matrix>
• all methods now take u32 instead of usize
• several renames to accommodate official naming conventions, basically use Mut/mut as suffix not as prefix
• ToOwned replaced in favor of libstd's From
• Tweak supertraits
• Remove rand and sample constructors
• Rename Mat::from_parts to Mat::from_raw_parts
• Remove from_elem, from_fn constructor from linear collections, use collect() instead

Behind the scenes

• detransmuteify the codebase
• remove cast panics from operators
• store dimensions as "u31" for easier inter-op with BLAS/LAPACK libraries
• DRY the code by making the mutable versions newtypes over the immutable collections
• tweak organization of modules to reduce privacy hacks

closes #18 closes #19 closes #23 closes #38